To use this list, follow this priority when choosing items:

Priority: Tree Whisperer > Dual Use items > Boss Melter Items > Swarm Melter Items = Damage Reduction Items > Reroll or Dissolve > Junk > FPS Killer >Idle Hands (don't get if you have 4 projectiles or more)

Use your judgment on an item when you believe it's been leveled enough and should be skipped in favor of an item in a lower tier. While this priority list works well in general, you will probably want to avoid putting too many points in certain skills with diminishing returns, like movement speed, and you'll also want to prioritize skills that tend to be high rarity over those with lower rarity to ensure you actually get the top tier of an item when you have the chance.

Abnormal Autopsy is an artifact that removes XP from the game and replaces it with random item drops. It has a positive score multiplier which would imply it has a negative effect, but when you try it you'll notice that it can carry you rather far. I've previously thought that since you get more items from it in general that it's superior to XP. Recently however I've been trying strategies that reroll or dissolve any bad item from the game (i.e. useless item or item that impacts FPS/Screen clutter negatively). I compared an Abnormal Autopsy game where I took all items with an XP game where I only took good items at around the same stage (around 50). The result was that I had more items in the Abnormal Autopsy game, but when subtracting out the items I had dissolved I ended up with a difference of 11 items in favor of abnormal autopsy, which can be accounted for by the difference in time (20 minutes) and the 4 points in orb booster. Now dissolving an item doesn't refund 100% of xp, so I would have had more items overall in the XP run had I not dissolved any, but I took that game to stage 100 and I noticed at some point around stage 60 or so that my level was 111 and not moving up very fast. I ended the game at level 114.

My conclusions for this lead me to believe that if you are dissolving bad items (which at this point I 100% recommend, even if you use Abnormal Autopsy), an XP run will carry you better than Abnormal Autopsy until around level 60-70. Abnormal autopsy doesn't really fall below giving you at least one item per stage, and seems to randomly award many more even at high progress. So, based on this I'm assuming Abnormal Autopsy is the superior choice when you're going for stage 100+.

This item is necessary if you get past stage 5 or so. The earlier you can get it the better. Tree Whisperer drops items if you are sitting on a tree. The proc is about once per second and according to the dev it will only select one tree to proc on if multiple are touching you. The proc rate doesn't seem to change if you move quickly across multiple trees, though it's hard to tell without confirmation. The earlier you get this, the more items you'll have. If you don't get it you'll eventually hit a point where you can no longer get items due to how levelling scales. If you're using Abnormal Autopsy the game appears more generous later on and you can still get about 3 items in a stage, but you'll get more from Tree Whisperer on average. Unfortunately you need to get Tree Hugger before getting Tree Whisperer, and tree hugger isn't particularly useful especially with Abnormal Autopsy.

Items here are 2-in-1 use case for the next 3 tiers below. In other words they can be Boss melting and Swarm melting and Healing, or any combination thereof. These should be your first priority when they appear, at least until a point.

Priority: Tree Whisperer Tier > Energy/Time > Spirit of Mumsa > Slash > Mass > Boss Melter Tier

Salvaged Energy (AoE): This item hits 2 checkboxes, AoE and Healing. Salvage Energy tends to do enormous amounts of damage on the end screen. Since the attack is centered on the Gooby, it can be useful against bosses as well. At level 1 you'll do (50% * combo number) damage in a radius (based on your combo) around you. Level 2 will deal (50% * combo number) + (0.005% * combo number) in a radius based on your combo. These numbers seem small but they seem to add up, and the enemies within the radius just disappear. At level 3 the bonus damage goes up to 0.001% of your combo, and you get healing at 0.001% (1/100k) of the combo. The healing might not seem like much, but it will pretty much instantly cap your health if you have a good combo going. The final upgrade increases bonus damage to 0.015% of a combo, healing to 0.0015%, and adds an effect where you get 500 orbs at the end of a combo which frankly won't matter by time you can get to this level. Level this to 3 if you're using Abnormal Autopsy, 4 if not, and afterwards focus on other things below.

Spirit of Mumsa: This item is good for boss melting and damage reduction in the form of movement speed. Each level adds 1 of the base numbers here for everything exluding frenzy duration to the effect, making it good to upgrade. The boss melting comes from an assumed source of damage the item inherently adds and in the form of movement speed damage from Yellow Sapphires. Each attack has a 1.5% to proc Spirit of Mumsa, which will make you enter a frenzy indicated by little red dots that surround the Gooby. The effect adds +3 base damage (before calculations) to every attack (including weak ones such as a slash chain or Splinter, making the combo of these two items good) and +10% to speed. At level 4 you'll have a 6% chance to frenzy for 3 seconds, with damage +12 and movement speed +40%. Put at least one point here before other upgrades, but I'd advise against putting more than 3 here and 5 in capsule.

Slash: This is a passive good for dealing with swarms and dispatching bosses. It does require some crit, but the 3 crit upgrades are good enough to make this a very desirable item. At level 1 it's just for swarms, which is what you want early on anyway, and has a 20% chance to proc on a crit. When activated it will hit up to 2 slashes on a nearby enemy (including the enemy that the item activated on) dealing 50% of the crit damage. Level 2 gives it a 40% proc chance on crit, and increases the damage to 75% of the crit. Levels 3 and 4 add 1 slash per level. Level 5 might have a typo in it, stating it causes up to 3 slashes. I'm pretty sure it adds another slash, since every level after 5 does that. The more important thing here is each slash is considered a guaranteed crit. This means you can get an infinite chain of slashes, at least until damage goes below 1, if your crit is high enough. At level 5 you can see the damage it does to bosses pretty easily. It's effect acts very much like an AoE on the swarm, but isn't affected by AoE radius. Adding more levels past 5 is only good if you have the damage for it since each follow-up slash reduces damage by another 75%. Leveling this to 5 is your priority, then you can safely ignore it.

Tranquilizing Mass: This is a good boss melting item, a good damage reduction item, and good for keeping swarms away from you. This item starts modest and becomes great. At level 1 it looks pretty bad, you get an orbiting mass that does a little damage and slows enemies. At level 5 you get 5 orbiting masses that on-hit each have a 15% chance to give you a shield that provides 25% damage reduction for 3 seconds. After level 5 you can upgrade shield chance up to 25%. The masses get buffs from damage upgrades and proc effects that aren't "Initial Attack" related, and they orbit fast effectively turning the radius around you into a buzz saw. Around level 10 or so there is falloff as far as adding more masses goes. Focus on leveling to 5, then move to other upgrades below.

Items here mainly add damage to a single target, so any boss/miniboss/elite. Elites shouldn't be a problem if you follow the tier list, and minibosses aren't dangerous enough to prioritize damage for, but bosses have a bunch of ranged attacks especially when they start mutating, and eventually a hit from these will one shot you. That makes one shotting bosses before they can do the same to you a high priority.

Priority: Dual Use Tier > Crushed Ruby > Crumbled Sapphire > Yellow Sapphire > Brisk Capsule > Sonic Howl > Girthed Up > Condensed Power > Obliteration > Hardened Tip > Citrine Crumbs > Swarm Melter Tier

Crushed Ruby: This is your main source of crit chance beyond the starting bonus you unlock. Levels 1-3 give a crit chance of 10% > 17.5% > 25% with a crit damage multiplier of 150% > 190% > 225%. Levels 4-6 change Ruby to Cracked Ruby, giving crit chance of 25% > 35% > 40%, crit damage of 225% > 250% > 300%, and a Bleed stack (DoT) lasting 3 seconds of 20% > 35% > 50% of the crit damage. Level 7 changes Ruby to Immaculate Ruby, giving crit chance to 50% (where it remains), crit damage of 375%, and giving crits a 1% chance to proc cardiac arrest which instantly kills the target. Further levels add +55% more crit chance. Immaculate ruby is very good and should be prioritized, so focus on getting it to level 7 then go for other things below.

Crumbled Sapphire: This increases all damage sources. Lv 1-3 Increases damage by 15% > 30 > 60%. Lv 4-5 Fractured Sapphire Increases damage by 85% > 115%, all damage has 2.5% > 5% chance to deal double damage. Lv 6 - 7 Increases damage by 155% > 205%, all damage has a 7.5% > 10% chance to deal double damage. Deal an additional 1% > 2% damage per point of damage dealt up to 100% > 200%. Further levels increase damage by another +10%. The Pristine Sapphire effect is effectively another damage multiplier on top, so it's worth prioritizing until you have this at level 7, then move on.

Yellow Sapphire: Adds a flat +0.2 base bonus damage to all attacks per curent movement speed. This is automatically more powerful than Hardened tip since .2 * movement speed of any Gooby is greater than 1. It also combines wonderfully with Capsule and Spirit of Mumsa. Put at least one point in it to start with. The successive levels decrease the bonus, but it's always better than Hardened Tip. Balance this with movement speed, and otherwise move on.

Brisk Capsule: This is a dual purpose item when combined with Yellow Sapphire, which is why its here instead of in the Damage Reduction tier. While it's nice to have more movement speed, there is such a thing as too much movement speed. This limits you as to how many points you'll want to put here for damage. I'd advise against putting more than points 5 in capsule and 3 in Mumsa.

Sonic Howl (AoE): Originally I had this in the Swarm Melter tier, then I realized it does enough damage to bosses to bump it up. The first item I ever got was Sonic Howl so I had assumed for some time that it wasn't very good. That was wrong. Sonic howl keeps damage pace with other AoE affects and instead of activating on kill, it activates every second starting at level 1 (much faster at higher levels). It centers on your Gooby, so at first it won't be doing much in the way of long distance damage. Because of this you will probably need a chain attack option when you don't have many upgrades. When you do have upgrades though, Sonic howl is effectively a shield that surrounds you and ensures that any weaker enemy won't be able to touch you. This is also why I consider it a reliable boss killing move, it consistently does damage within a range of your Gooby and provides an AoE damage source. Prioritize it over other AoE moves, and I would highly recommend using this as your only other AoE besides Salvaged Energy/Time. Seismic Tsunami is really good so try getting this to level 7 before moving to other things.

Girthed Up: Increases AoE range by 15% per level. This is actually a fairly large range, and not too many points later you'll have screen-wide AoE procs, hitting both bosses and swarms. The effect is better against swarms but eventually AoE will be a major source of damage for you, much more than projectiles.

Condensed Power: Increases AoE damage by 15% per level.

Obliteration: This is a weird ability and until some numbers come out on it this is where it's going. The description seems to imply that it can chain until it hits the HP cap, though it's an open question whether the HP% is taken before or after hit calculation happens. I'd assume before, otherwise this would rarely proc. I asked on the forum what the level 3 ability is supposed to mean, and I play tested some to try to figure out how effective this item is on its own. Since it's taking the damage of another attack and multiplying it, this item sucks by itself. However when I have a longer run this item tends to account for at least 10% of total damage, so I'm pretty sure its getting about 20% of the total damage of all the attacks stronger than it. Hopefully that makes sense. At Levels 1-2, damaging enemies above 95% > 90% hp has a 20% > 25% chance to deal 75% > 115% of that damage again. Level 3 turns the item into Post Mortem Obliteration, damaging enemies above 80% has a 35% chance to deal 150% of that damage again. If the target dies, an effect called Post Mortem Obliteration will proc, which gives a 100% boost to all "On Death" effects (Fire, Exlposive Blobs, or some worthless skills further down) meaning they have 100% proc chance. Not sure how long this effect lasts.

Hardened Tip: Gives a permanent +1 to base projectile damage. This does affect all projectiles in the game (i.e. initial attack, dizzys ball, splinters, needles, chain, etc). No idea if this affects Tranquilizing Mass.

Citrine Crumbs: Increases attack speed, note that this doesn't increase projectile movement speed so it isn't particularly useful for swarms. Early on the upgrade acts normally, but in the current game the projectiles slow heavily once your FPS starts to decrease, so this item becomes worthless at that point which is generally around level 10 or so. Levels 1-3 increase Attack Speed by 10% > 20% > 35%. At levels 4-5 Citrine Changes to Broken Citrine, increasing attack speed by 50% > 65%, and providing a 15% > 25% chance of cauzing a status called Frenzy which temporarily increases attack speed by 5% > 10%. This frenzy isn't the same as the Spirit of Mumsa frenzy. Level 6 changes Citrine to Flawless Citrine, increases attack speed by 80%, keeping the same prior stats, and adding a double shot to every 20th shot. Another upgrade will take that to every 10th shot. There isn't much special about Citrine, and it looks like there is a cap on attack speed so only prioritize this if you are definitely attacking too slow early on, otherwise forget it.

Items here focus on spreading damage to multiple enemies, such as in the case of chain attacks, on-hit proc effects, or AoE attacks. Since most enemies will die in one hit we want to prioritize this for swarms. Note that even the lower ranked items in this tier have their uses and can do decent damage. Focus on one AoE effect to its max level at a time, so hopefully Sonic Howl if you're lucky enough to see it before these.

Priority: Boss Melter Tier > Chain = Soft Blobs > Damage Reduction Tier (as needed) > Strange Fruit > Reroll or Dissolve > (ignore these if you have Sonic Howl or intend on getting it) Fire/Implode

Chain (Projectile, Initial Attack): Effectively +1 projectile with an initial attack bonus after the bounce.

Soft Blobs (Projectile, Initial Attack): Effectively +1 weaker projectile that still counts as the initial attack.

Strange Fruit: Only get if more range is needed. Eventually you'll just end up putting points here. I think the item is intended to affect luck, and the dev confirmed that at the very least the Roulette rolls now work properly with luck. Nobody has been able to confirm what luck really does or how it works in this game.

Fire (AoE): Procs on kill. Third upgrade chains. Weaker than Implode/Explosion but easier to upgrade. Use Sonic Howl instead, it's less busy and more effective when fully leveled.

Implode (AoE): Procs on attack. Has far more damage and kills than fire. Chains less and procs more than the other two here. Has good final tier and looks kinda cool. Use Sonic Howl instead, it's less busy and more effective when fully leveled.

Items here help to reduce, avoid, or heal damage. 4 of the items that might otherwise land here, Capsules, Recycled Time, Tranquilizing Mass, and Spirit of Mumsa, are listed in higher tiers due to multiple effects, leaving us with one item in this tier. The usefulness of these effects is reduced if you have at least one point into healing fairy. Damage reduction with the current set of upgrades only really matters so long as you can't be one-shot or otherwise killed in under a second. Most of the defense therefore comes from offense. I expect that if the devs continue to work on the game there will be more items added here.

Thick Hide: This upgrade is mostly noticeable because it will add to your healing, the damage reduction is excellent at the cap of 50% but if you never pick this up you'll have a hard time noticing a difference in terms of damage taken since you'll be a powerhouse that only bosses can actually touch. That said I would recommend putting points into this as needed, and since it takes 7 upgrades to get to Spikey Discharge you'll want to take your opportunities getting this if you need damage reduction.

These are items that don't really add to your arsenal, have much better alternatives, or just plain suck. You'll want to fully upgrade some of them for the encyclopedia entries but that's about it.

Priority: Damage Reduction Tier > Strange Fruit > Reroll or Dissolve > Fire/Implode > Soul of Amam > Orb Amplifier > Silly Saucer > Bloberang > Essence of Zigrid > Spikes > Halo > FPS Killer > Idle Hands Tier

Soul of Amam (AoE): 5% chance to fire off a shade that flies through enemies, any enemy it flew through will explode (not die, just explode) when the shade flies off the screen. It does fairly low damage that is quickly surpassed by any AoE listed above. It does clutter the screen, which if you can't distinguish where your item drops, trees, goobies, or enemies are you should consider avoiding this.

Orb Amplifier: At level 4, 30% more XP and a chance for duplicate orbs. That's as good as it gets because it's capped. The big problem with Orb Amplifier is that it doesn't keep up with XP scaling in the game, rendering it effectively useless. You'll get a level or two out of it in a run, that's about it. It won't affect the XP from dissolving items which is your primary XP source late in a run. More importantly, while Abnormal Autopsy is available to you and as long as it remains in its current state this upgrade is rendered pointless. Abnormal Autopsy continues to give out items as you progress in the game, distributing 1-3 per stage even very late in the game while getting rid of Orb Amplifier as an option in the game. Abnormal Autopsy also provides a score boost rather inexplicably, so until it gets a nerf there's no reason to avoid activating it and this item won't even show in your game.

Silly Saucer (Projectile): Rotates around you and flies off when hit. Not very strong. The upgrade adds a saw that goes across the screen sometimes. Not worth getting. It does clutter the screen, which if you can't distinguish where your item drops, trees, goobies, or enemies are you should consider avoiding this.

Bloberang (Projectile): Generated from attacks, they fly in an arc where they generate and do very small damage. The upgrades will spawn more Bloberangs and make it so you can relaunch them by catching them, which you are totally going to try to do because you don't have anything better to do. It does clutter the screen, which if you can't distinguish where your item drops, trees, goobies, or enemies are you should consider avoiding this.

Essence of Zigrid (AoE): Spawns goo balls above random enemies on attack. The animation is messy and distracting, and the goo balls don't do much damage. It does clutter the screen, which if you can't distinguish where your item drops, trees, goobies, or enemies are you should consider avoiding this.

Spikes: Totally worthless, they do barely any damage when fully upgraded.

Halo: You can make this work by maintaining a lot of HP loss, in which case you are doing a specific build that requires this item. Otherwise it's useless since you'll quickly heal to full.

This section has been more recently created since many items in the game are known for reducing FPS significantly. Taking any of these items will impact your FPS negatively and some will make the game so slow that you're bound to lose without seeing what killed you. Maybe the dev will fix these and optimize the game at some point, but until then make sure you avoid these items so you aren't running at 10 FPS at stage 50. This list has been put together by the community, and I've already discovered that Hailstorm at level 1 doesn't affect my FPS at all, but I'm choosing to trust this list since as I said, I had no FPS problems when ignoring these items. If you feel like any of these needs correction feel free to leave a comment. One other thing to note is that XP orbs also negatively impact FPS, but all you can do in regard to that is to use Abnormal Autopsy. I'm leaving the item descriptions I previously made here.

Ghost Blobs (AoE): Procs at low 5% > 10% on kill creating a ghost blob that blasts in a radius around it every second or so for 5 > 10 sec. This upgrade has 2 levels to max (nothing happens above level 2) and is very easy to upgrade compared to the other AoEs below, chaining a bit worse and acting a bit more unpredictably so that it never really matches their damage but getting more effective as the game progresses at clearing the area around you. After trying it a bit more I've come to realize it's at least as good as the other AoEs in the swarm tier, but not anywhere near as good as Sonic Howl/Seismic Tsunami. Ghost Blobs is attributed to the largest FPS drop in the game.

Splinter (Projectile): + 3 projectiles, will chain once you get splinter storm. Reportedly has a large impact on FPS.

Thousand needles (Projectile, Initial Attack): Only get if you need something that chains at the beginning of a run. Reportedly has a large impact on FPS.

Hailstorm (Projectile): Hailstorm is centered around the Gooby. Not great for this reason. Reportedly has a large impact on FPS.

Frostbolt (Projectile): Sometimes a frost projectile will shoot out from other projectiles and it goes through enemies. The upgrades are decent, but this isn't predictable in any way and isn't very strong. Reportedly has a large impact on FPS.

Wiggling Worms (AoE): On death worms will move away from the dead enemy and move through other enemies, damaging them. Not particularly strong, doesn't chain well and doesn't seem to increase its AoE range. Reportedly has a large impact on FPS.

Goo (AoE): Misses more often than it hits, creates a lot of distracting messy visuals that you're better off without. When it hits it does decent damage, but that's rare. Reportedly has a small impact on FPS.

Explosive Blobs (AoE): Procs on kill. Last upgrade can chain. Has most kills for AoE at the end screen.

Dizzys Ball (Projectile): Extra projectiles from balls that go through walls. These aren't counted as an initial attack, but are serviceable as a projectile. They can ricochet but they don't add all that much damage. Reportedly has a small impact on FPS.

Chain Lightning (Projectile): Only get if you need something that chains at the beginning of a run. I haven't confirmed its impact on FPS, but it gets busier at higher levels.

Other items worth mentioning that reportedly impact FPS, but are too good to sacrifice: Sonic Howl, Chain, Tranquilizing Mass, Low Viscosity. If you run into problems with these just limit the points you invest except for Sonic Howl, if you take it at all it will impact FPS.

Idle Hands is so bad that it gets its own shout-out. Idle Hands is the worst item in the game, providing permanent debuffs after you have 4 projectiles. Before you upgrade your starting projectiles it can be useable, but you should be prioritizing your number of projectiles before any other stat. There is math among the Steam discussions that back this up, so until it's reworked just avoid it at all costs.

Per user request, the following is a list of the items you'll want to take and how many you'll want to take.

Tree Whisperer > Energy/Time (4) > Spirit of Mumsa (3, you get too many and your guy is impossible to control) > Slash (5-10) > Mass (5+, you'll want at least 15 or so later on) > Crushed Ruby (7, the rarity of this item increases to Yellow so prioritize when at higher rarity) > Crumbled Sapphire (7, the rarity of this item increases to Yellow so prioritize when at higher rarity) > Yellow Sapphire (At least 1, but really as many as comes your way) > Brisk Capsule (5, don't get too fast) > Sonic Howl (7, the rarity of this item increases to Yellow so prioritize when at higher rarity) > Girthed Up (As many as it takes to cover your viewable area with AoE, even then it seems good to keep going) > Condensed Power (At least 1, preferably more since this upgrade isn't in the Stat roulette) > Obliteration (3, Red, Red, and Yellow rarity) > Hardened Tip (1, get more if projectile damage is limiting you) > Citrine Crumbs (7, Ideally you will be able to skip this but that is doubtful) > Chain = Soft Blobs (4 in each, but keep FPS in mind and don't bother putting points here after your Crit/AoE takes over) > Spiky Hide (7 and no more than 7 due to diminishing returns, the rarity of this item increases to Yellow so prioritize when at higher rarity) > Strange Fruit (However many you feel you need, I usually skip it entirely since projectiles never hit later in the game and luck is indeterminate) > Reroll or Dissolve > Everything Else

Due to lag and screen clutter, it's better to dissolve items with visible affects that aren't useful even in Abnormal Autopsy, where you get nothing for dissolving. In Abnormal Autopsy you might as well take Halo up to level 2 since it's passive, though don't level it up more because it will start raining spears down. As far as Orb booster goes, see its section and determine whether you want to use it or dissolve it. I'm not sure it matters much and it won't affect the XP from dissolving items.