This guide is going to be fairly simple. I'm going to rate augments based on a system of tiers :

• S-tier: should always be bought or picked up, whenever possible.
  
• A-tier: I would consider keeping them if picked up free, or even buying them in some situations, but most of the time it's just something you'll avoid (or sell).
  
• B-tier: Very situational, usually bad.
  
• C-tier: Terrible. Basically free scrap if you get them, because they just don't do anything useful.

Of course, I'll explain the reasoning behind every ranking. I will not, however, detail the rarity or price for each augment – there's the wiki for that, and it's not the point of this guide.

Here is a non exhaustive list of criterias I use to rank augments:

• Beneficial to scrap earnings.
  
• Increases offensive capabilities significantly (similar to an extra system's value in terms of given possibilities or raw power).
  
• Increases defensive capabilities significantly (similar to an extra system's value in terms of given possibilities or raw power).
  
• Has several and decently common* blue options, i.e. options with high scrap rewards, or stuff (mostly weapons or crew), and decreases the likelyhood of you getting a nasty outcome in some events.

* Several and common, because a lot of bad augments have a blue option in one very specific event, and while this blue option is cool when you get it, it doesn't make the augment any better.

You will notice there is a somewhat high gap between S-tier and A-tier. S-tier seems, well, what you'd expect from S-tiers, which is a "must-have". A-tier however, in my definition, probably feels like B to you. And so on for other tiers.

It kind of is intended. The thing is – in FTL, most augments are bad or situational. And that's the case because they're not critical to your win conditions, like systems or weapons are.

The notion of important purchase seems important to explain this. Important purchases, to me, are :

• Buying systems. Make no mistakes, finding your systems (which are, usually, hacking, cloaking and MC) is what will win you the game consistently.
  
• A good weapon to add to your setup.
  
• A critical system upgrade (the most notable one is level 2 shields by the end of sector 1 ; after that, systems upgrades become already less significant)

Exception made of Long Ranged Scanners, you should never buy an augment instead of an important purchase. And exception made of S-tier augments, or some situational ones like pre-igniter or zoltan shield bypass, you should probably always sell an augment if it enables an important purchase.

Selling an augment is always a quick boost to your scrap (25 to 40 for most augments). And that can often enable important purchases. Which is why it's often correct to sell an augment you got for free, even if it's B or A.

There are two mechanics you should be aware of when it comes to buying and looting augments:

• You are limited to 3 augments per ship and can't store them in the cargo hold. Buying augments will not be possible if you have three already (they can still appear in stores) and you will have to toss one out (with no scrap benefit) if you loot a fourth.
  
• If you loot a duplicate augment it will be converted into 25 scrap, unless it's a stackable augment (like Scrap Recovery Arm, or Automated reloader).

• Long Ranged Scanners

Surprising absolutely no one. This augment is 100% the best in the entire game. It is ridiculously good. It's pretty cheap (30 scrap), which means you can afford to buy them after a few jumps (and with some ships that have extra stuff to sell, instantly) and it makes you earn so much more scrap. That's the value of knowing what are at nearby beacons.

You get to know which beacons are fights and/or hazard, which helps you avoid those nasty boarding events (like the sun flare with no ship detected), find fights, avoid dangerous fights (pulsar when you don't have hacking). You can also track some specific events, like the lost rock cruiser (nebula with ion storm and ship), storm items (nebula with ion storm and no ship) or generally interesting quests.

Two very interesting quests to find are the Zoltan Peace Envoy in Zoltan Homeworlds (for either Zoltan Shields or the envoy, the former being a lot better) and the Second Rebel Flagship in Rebel Stronghold (for the free weapon, resources, and two extra jumps). Those quests always start on a beacon with no ship detected. Which means, with LRS, you can track down where you have a chance to see these events and decide whether you want to commit to the search.

At any rate, it's an insanely good augment. Always buy, never sell.

• Zoltan Shield – Not purchasable

You might think only the Zoltan ships can have this one... But in fact, when completing the Zoltan Ship quest, there's a one in four chance to get the augment in place of the envoy. And honestly, it's worth looking for. This shield blocks any enemy projectile including missiles (which is already great), as well as hacking, teleportation, mind control and boarding drones so long as it's up. It does nothing on boarding events however.

This shield increases your defense by a significant amount. It's much more valuable than a standard layer of shield, and not taking any damage from small missiles at the beginning of a fight is really good. if you have a good volley, you destroy the enemy weapons quickly, and they just never fire.

• Automated reloader

Speeds up your volley by 10 percent. Stacks with other reloaders and crew skill (but not in the way you'd expect – check the wiki for the math).

It's not bad, and I'd keep it if I got it for free (unless selling it enables an important purchase). But unless you have loads of scrap it's not really worth the purchase on any setup, really. It's not even really good to beat a small missile's loading time, because in the early game there are more important purchases, and in the late game, you should have systems to deal with them.

• Weapon pre-igniter

Weapons are ready to shoot as soon as you exit FTL jump. The longer your volley's charge time is, the better the pre-igniter is. Thing is, usually, you want to have a fast volley, and long-charging weapons tend to be bad (Beams, especially the Halberd, are a notable exception). Every now and then, you're in a situation where pre-igniter is interesting. Just remember it's 120 scrap, which is almost as expensive as cloaking. So this purchase should be very carefully considered.

• Reverse ion-field

It actually is pretty good. Usually it won't make a big difference, but the triple ion artillery of the Flagship (and some ion weapons on enemy ships, especially if combined with beams) can be pretty dangerous in phase 1. I still wouldn't buy it unless I have scrap to spare, but there's an argument to keep it if received for free.

• Shield charge booster

It's very similar to the Automated reloader (especially because it's also stackable), but it just feels pretty underwhelming, even if you get it for free. While the bonus is nice to have, it just lives in the shadows when you can just hack weapons, cloak the dangerous ones, destroy the enemy weapons (or even the whole ship) with a fast volley, etc.

I'd never buy it, and basically sell it unless I don't have any important purchase coming.

• Zoltan shield bypass

Basically only good if you're a boarding ship and mostly for phase 3 of the Flagship.

• Reconstructive teleport

It's only a gain of time, one way too expensive for it to be justified (70 scrap, which is almost the price of a system like hacking). The only time I would ever buy this is one Slug B, which starts without a medical unit, if I'm confident to use my teleporter as one, and to get 4 systems (Hacking, Cloaking, Teleporter and MC, which is usually impossible).

• Stealth weapons

Absolute garbage. Just useless. Sell them.

• Explosive replicator

Missile weapons are mostly bad and should be avoided, which means explosive replicator will in most of the time be useless.

When you're using missiles, you should only have one missile weapon, and running out of missiles is a rare worry (unless you're Slug B or Rock A). Even then, I would always sell this augment and buy actual stuff.

• Hacking stun

Pretty useless. The locked doors with hacking are enough to kill people when you need to. While hacking should almost always be sought out, there's no reason to use this augment with it.

• Defense scrambler

This augment only affects Anti Drone and Defense drone (not the Overcharger, neither drones inside the enemy ship). So it's basically useless to ensure hacking – there's the depower-repower trick for that – and usually your weapons should be enough to overcome any defense drone setup. This augment is basically 40 free scrap if you get it.

• Repair arm

It decreases your scrap earnings for potentially unwanted / unnecessary repairs. Horrible. Sell ASAP.

Repairing to full health is bad because you can lose value on repair events, including the guaranteed 10-hull repair at the beginning of sector 8. Instead, you usually repair to 20/23 points of health to get value out of free repairs from events.

• Emergency respirators

Pretty useless from a defensive perspective. They theoratically provide room to board oxygenless ships but there are far better answers (level 2 teleporter, lanius boarders, clone bay, or just weapons).

• Fire supression

Useless and incredibly slow. Venting and Engi * are the proper responses to fires, not this.

* Engi are better than Rock to put fires out because they have repair bonuses, and Rock are super slow so the fire might spread out of control by the time they get there.

• Backup DNA bank

This is mainly meant as a safeguard for boarding ships. It doesn't do anything in events where the clone bay will not revive a crewmember, and has very few usages in terms of events, if any.

I think you shouldn't lose crew members to a depowered, deactivated or broken clone-bay, ever. In my opinion, the proper response is to learn to play around what makes you lose crew, rather than buying this augment. Some examples :

• Refresh your crew (vent them to death and then clone them) before jumping when they're low on health.
  
• As much as possible, avoid having a cloning process during a combat, unless you can 100% prevent the enemy weapons from hitting your ship (e.g. turtle strat with level 3 hacking on the weapons and level 2 cloaking, where enemy weapons never fire).
  
• If you're about to have a cloning process during a combat and there's a chance your clone bay gets broken, have 2 Engi in the room ready to do repairs.

• FTL recharge booster

Pretty useless, really. You shouldn't have to run away from fights, unless you're close to death, in which case having this augment most likely will not save you.

• FTL jammer

Again, pretty useless. In the early game, this may make a difference if you have no systems, but the thing is, not buying it / selling it (if received for free) will lead to more efficient scrap usage.

• Advanced FTL navigation

Hands down the worst augment in the game. Going back to a previously visited location is just wasting a jump and you should never have to do that.

• Distraction buoys

First case of the "augment that looks good on paper". The problems with this augment are :

• It only activates at the beginning of a new sector, which means you will only get 6 extra jumps (one in each sector from sector 2 to sector 7), 7 if you get the Crystalline sector, which obviously almost never happens.
  
• There is no guarantee that the extra jump will actually have a positive outcome.

So buying it is a terrible idea. If received for free, I might keep it, but it's really not that good.

• Scrap recovery arm

Second and most critifcal case of "augment that looks good on paper". It's actually awful. Why? Well, Scott explains it better than I do in his video, but basically, it's way too slow and buying it can put you behind in terms of important purchases.

Even if you get one for free, usually selling it ASAP provides more value because you get a more useful purchase earlier.

• Drone recovery arm

Usually, you will run out of drone parts because of hacking usage, and hacking drones do not get recovered by this (neither do boarding drones, for that matter). So, it's pretty pointless, really. Better to buy drone parts at a store (there's always a minimum of 2) than this.

• Battery charger

It's just very useless, especially because the battery's cooldown is nullified when you jump (which is not the case for other systems). The battery is meant to support your power usage, you shouldn't have to actually rely on it to power critical parts of your ship (unless you're Zoltan C, and even then I wouldn't buy it).

• Lifeform scanner

With experience you can tell what's going on on the enemy ship just by looking at doors and knowing how the AI works, so this isn't really useful, unless you have MC and no sensors or slug crew (in which case you should just not buy MC and have something else instead).

Some augments can't be purchased at stores and can only be obtained through events or because your ship starts with it. I already ranked the Zoltan Shield as S-tier. Other such augments are :

• Engi med-bot dispersal (Engi A and Rebel attacking engi event)
  
• Rock plating (Rock ships and Rock cruiser quest)
  
• Titanium system casing (Stealth A and Stealth cruiser quest)
  
• Drone reactor booster (Engi B and Virus event)
  
• Slug repair gel (Slug ships and Slug cruiser quest)
  
• Mantis pheromones (Mantis ships and Mantis cruiser quest)
  
• Crystal vengeance (Crystal ships and Crystal cruiser quest)

All of these are basically useless or irrelevant, and should be sold early for a quick scrap boost.

A comment to add? A mistake you think I've made? A suggestion?

Please let me know in the comments section below!

Thanks for reading the guide and have fun on FTL!