Frankly, I'm going to piss people off regardless of what advice I give them, but a lot of people have pointed out that playing one class (and only one class) is an easy way to burn yourself out of the game and hinder your overall potential as a DRG employee. This is true, and I wholeheartedly agree: you are not required to find a class for your main, and ideally, you shouldn't. The only reason you'd be interested in maining a class (at least for a while, anyway) is to get access to overclocks as quickly as possible. This is where a lot of arguments come from saying things like "driller doesn't have high-target damage" or "engineer/gunner don't have as much firepower as the other". The bottom line is, any class can be really good at mostly everything... with the right mods and overclocks.

But for anybody reading this guide, you're likely just starting out and probably haven't even promoted one of your dwarves yet (or you're at least getting close to promoting one of them). You don't have access to overclocks yet, and while mods can do a little bit of legwork in helping your class specialize and adapt to their weaknesses, those overclocks are the primary factor in most (if not all) builds. In light of this, I'm talking about a class's strengths and weaknesses based on what they have pre-promotion, without overclocks, with only the gear you have and whatever mods you might have unlocked as you level up. There are still some things that remain consistent with some classes once you get your hands on overclocks (like the vast majority of engineer's loadouts being ammo-costly), but by the time you get these overclocks and start working towards builds, a lot of issues that may discourage you from playing one class might go away once you can start making builds.

Driller was an extremely unpopular choice for me because of how underwhelming he was in terms of damage. That got progressively better and better as I got more mods, but because I had already promoted one of my dwarves, by the time I was able to put an overclock on one of his guns, I was able to turn Driller from a respectable crowd-controller to a crowd controller that also has really nice DPS. Anybody having a similar issue with other classes might be interested in sticking to their favorite, promoting that class, and then going to that less-favored class to work towards a build that allows them to play the way they want...

...and besides, you need to promote a class at least once in order to use that class in the Deep Dive, which is the best way to get overclocks, so giving yourself that flexibility by promoting all your dwarves is very important.

-classes can make up for their weaknesses eventually, but that requires tools you don't have access to right away. Pick a class that suits your playstyle, then when you get those overclocks, you can adapt the other classes to your playstyle once you bring them up to high enough a level to mod them.
-The majority of arguments made in the comments can be turned down because we're talking about what you have at base kit. I might be wrong about a few things, and I own up to that, but it is possible for every class to do a little bit of everything, with the right mods and overclocks. If you're reading this guide and you're new to the game, you don't have those tools yet.
-This guide is here to help you figure out which class fits your playstyle and how you can effectively level up that class so you reach your promotion as quickly as possible (recommended missions, hazard levels, etc.) I didn't know it wasn't clear before, but I'm putting it out there now.

SO WHAT IF I LIKE REALLY BIG GUNS?
~Gunner

The gunner is the very first class you're introduced to when the game drops you into the tutorial section. There is hardly anything about Gunner that isn't appealing: he's got big guns that do big damage, options for both long range and short range combat available to him off the bat, and a shield that not only keeps the bugs off you for a few precious seconds, but also allows you to regenerate your shield at ludicrous speeds. A well-prepared gunner can handle any combat situation, and from level 1 with zero mods on your guns, you already got it.

The gunner can fit just about any role as far as killing bugs are concerned. His minigun, autocannon, and rocket barrage launcher are equal in power dealing with both hordes and large, tanky enemies in turn. The Gunner has so much firepower that he can even consider mods that are normally a no-go for other classes, such as blowthrough rounds (penetrating targets to hit more targets) or armor breaking (smashing armor easier and dealing more damage with the breaking shot).

His only real weakness comes with his traversal tool, which comes off as the least useful compared to the other three classes. While Gunner can solve some terrain problems with his zipline gun and utilize it as a safe getaway from some bugs, it is a cumbersome tool that lacks the creative use and versatility other classes tap into with their traversal tools. There are still some applications that make the zipline good in its own right, and they are especially useful for transporting heavy items from the distant caverns to the Minehead, but limited ammo on the zipline means you have to be careful and considerate in setting up your ziplines.

Main Gunner if you like:
+ Having access to strong, versatile, and ammo efficient weapons from start to finish
+ Killing both hordes and high-health single targets with ease
+ Being the anchor of the team

Don't main Gunner if you:
- Hate slow mobility characters
- Want a cure-all solution for navigating some of the trickier cave formations

Recommended missions for Gunner:
- Mining Expediton
- Egg Hunt
- Salvage Operation
- Point Extraction*
- Elimination/Industrial Sabotage
- Escort Duty

Recommended hazard level when playing solo: 3+

*Point Extraction is only recommended if you are playing solo (since Bosco can easily mine and transport Aquarqs for you) or if you're playing with well-coordinated friends.

Quotas and objectives to fulfill! Let's get 'er done, lads!
~Engineer

The Engineer is the most versatile class. Like the Gunner, the Engineer has access to strong firepower off the bat, especially with his automated sentry turrets as his support tool. While the Engineer starts out with weapons that are only really effective at close range, as you level him up, acquire mods, and eventually get your hands on those sweet, sweet overclocks, he can specialize into whatever role you want to fill in, and still be able to assist the team with your sentries laying down fire. His traversal tool shoots out platforms which can also be modded to absorb fall damage, allowing him to make bridges, ledges, stepping stones, landing platforms, anything to get the team to where they need to be without shattering their knees.

Note: Engineer and Scout are a very special pair. With Scout's flare gun and grapple hook, and Engineer's platform gun, there's not a single vein of ore that will go untouched, allowing you to maximize your collection of Nitra for those ever-so-precious resupply pods.

The Engineer's firepower is absolute, even on par with Gunner, but not very many (if any) of the Engineer's weapon loadouts are very ammo-efficient. Of course, Ammo efficiency can be "efficient" if you only need one shot to kill a whole bunch of bugs or a tanky Oppressor, but those who like to mag-dump whole magazines into bugs will find themselves short on ammo fairly quickly with Engineer. As a result, playing Engineer requires you to be conscious of how you're spending your ammo, and making sure all your tools of destruction get equal use so you can get the most bang for your buck and replenish the most ammo from resupply pods.

Main Engineer if you like:
+ Destructive force in modest packages
+ Swiss-Army knife type versatility
+ A multi-purpose platform gun that can benefit your teammates and not just you
+ Being the top in an Engineer-Scout relationship

Don't main Engineer if you:
- Struggle to manage resources and don't like versatility where most of the builds are ammo-inefficient
- Can't set up turrets in advance when clearing out caves or facing a swarm
- Don't want to experiment with weapon loadouts to find what you're comfortable with
- End up pinging that vein of Nitra for the 12th ♥♥♥♥♥♥♥♥ time because your mud-fuddling Scout isn't paying attention

Recommended missions for Engineer:
- Mining Expedition
- Egg Hunt
- On-Site Refinery
- Salvage Operation
- Point Extraction
- Escort Duty
- Elimination/Industrial Sabotage

Recommended hazard level when playing solo: 2+ (3+ if you're confident about your weapon builds and ammo usage)

Guys... I just figured out how to make the Power Drills drill through minerals! Take notes before I forget... DAMN, I LOST IT!!!
~Scout on his third round of Smart Stout

The Driller is to Deep Rock's classes as ice cream is to comfort food. His drills drill through everything... except minerals, for some reason, because Management won't give us any faster alternative to mining other than our pickaxes. In a game where the ground is completely destructible, the mole man is king; the Driller can dig, tunnel, carve, and excavate just about anything to create shortcuts, grant accessible routes to difficult spots, make bunkers designed to force incoming bugs into chokepoints, and even move objectives like hacking pods and uplinks to more convenient spots. Where Engineer is the most versatile in combat, the Driller is the most versatile in shaping the environment to his team's advantage. The Driller can even use his drills as a powerful melee weapon, which easily stuns, deals damage, and inflicts fear into any bugs that try to give him the vibe check.

Driller's weapons, at first, leave little to be desired. Up close, Driller has his primary weapons, which are extremely good at dealing with hordes; by themselves, they are incredibly weak against high-health targets. Driller's secondaries can be modded to synergize fairly well with his primaries, and make up for his lack of range by allowing him to hit distant targets, but Driller's secondaries are incredibly weak.The Driller does have access to explosive C4, as mentioned before, and it can be modded to deal tons of damage... but it's a highly ammo-inefficient option compared to what Engineer, Gunner, and especially Scout have to offer. Regardless, Driller is one of those classes that starts out weak and can come off as ridiculously powerful once you have the right mods and overclocks.

The Driller is the closest you can get to a melee class, and he does the job fairly well... even his Impact Axes count as melee kills, if you want to take advantage of the Vampire perk that grants you a smidge of health whenever you kill bugs with melee attacks.

Main Driller if you like:
+ Harnessing the power of the elements (fire, ice, temperature shock, corrosion, etc.) to shred hordes and control the crowd
+ Utilizing what is arguably the game's strongest and most team-benefitting traversal tool
+ Being the other anchor for the team when the bugs get close and things seem out of hand
+ Exploiting the special interactions of elements (like how freezing airborne targets insta-kills, burning rival tech insta-kills, freezing the burning and burning the freezing causes temperature shock damage, etc.)

Don't main Driller if you:
- Enjoy killing tough, tanky targets at a ridiculously high speed
- Dislike starting out weak, as Driller's base kit isn't all that strong compared to other classes

Recommended missions for Driller:
- Mining Expedition
- Egg Hunt
- On-Site Refining
- Salvage Operation
- Point Extraction

Recommended hazard level when playing solo: 2 or below

Driller requires status ailments to trigger on enemies for most of his high-damage builds to work. Because of how difficult it is to proc these elements on bosses, Elimination and Industrial Sabotage missions are heavily discouraged unless played in lower hazard levels. I highly encourage that you promote Driller first and get a strong build for him before approaching Elimination missions with him! Driller is actually surprisingly good at Escort Duty missions because he can tunnel to caves and clear them out in advance before activating Doretta, making it easier to protect her as you only have to worry about bugs coming from one direction. However, the flying rocks are difficult for Driller to deal with by himself, so try not to solo Escort Duty as Driller if you can help it.

Yeah, I don't so much "scout" as make this operation possible.
~Scout

The Scout is the most self-sustaining class in the game... with notable exceptions. His support weapon, the Flare Gun, allows Scout to light up entire caves, helping his team identify threats from afar, locate veins of ore in hard-to-reach spots, and help the team scope out the caves before diving in. The Scout also has access to the grapple gun, allowing him to get anywhere with speed and panache. Scout can easily negate fall damage and escape danger with this tool, but it doesn't benefit the team in the most direct of ways, especially during the fight. He synergizes with the Engineer incredibly well, as the Engineer can shoot out a platform and have the Scout grapple to it to excavate ore in hard-to-reach places. The grappling hook also allows him to outpace the bugs, making him a decent distraction for the bugs to benefit the team and allowing him to kite the horde until it's dead if the Scout is playing solo.

The Scout isn't lacking in terms of firepower, either. His primary and secondary weapons prioritize precision and high single-target damage, making him ideal for getting behind tough bugs to hit them where it hurts (or getting the big bugger's attention so his teammates can do the same). His grenades offer supportive benefits, slowing bugs down and making them take more damage, freezing them solid, or even turning the bugs against each other with pheromone grenades. However, the Scout suffers the opposite problem Driller has: where Driller struggles to deal with high-health targets, the Scout struggles with hordes. The Scout's tendency to move ahead of his team can also land him in trouble, as he might get downed far away from the team or in a hard-to-reach spot, or he could get incapacitated by grabbers or cave leeches where his team won't be there to save him. As a result of getting easily overwhelmed and facing stealthy grabber-type enemies where his team can't support him, Scout requires a high skill ceiling to avoid these situations... with the right mods and fast-paced decision making, however, Scout can hold his own in a plethora of situations... it's the times where he does need help from his team, though, that are crucial for him to stick close.

Main Scout if you like:
+ Dealing massive damage to big and dangerous targets
+ Being beneficial to your team in an indirect way
+ A high skill-ceiling class that can handle any situation as long as you have the patience for Scout's shortcomings
+ Being a flying-monkey minion for Engineer that gets in all the hard-to-reach spots to gather minerals for your team

Don't main Scout if you:
- Find yourself easily overwhelmed by swarms
- Can't hit weakspots/feel pressured to hit weakspots in order to stay competitive with other classes
- Get downed easily in situations where you are alone
- Hate dealing with that long-eared Engineer who gives you crappy platform placement and expects you to mine minerals in a situation rigged to get everything from your waist down shattered from fall damage

Recommended missions for Scout:
- Mining Expedition
- Egg Hunt
- Point Extraction
- Elimination/Industrial Sabotage

Recommended hazard level when playing solo: Largely dependent on how you handle juggling your grapple to get out of danger and your weapons to exploit weakspots