Although most of the commands and abilities can be learned, there are 3 small classes in the game. Once you choose a class, the other 2 are locked out, and you can then learn the extra abilities of that class. It is possible to switch, but only if you do a full respec.
Obtaining a class is *very* expensive, costing a total of 60 level points to get everything. They're intended primarily for high level players, although midlevel players may want to take one in some cases. As with all things, there are of course exceptions to this - see Sonya's very unusual, but very effective, early support build with TFC.
There is no best class, although of course there are areas of the game that each excels in. Choose the class that best fits your playstyle.
The short version:Army of 1: Supercommander - You excel in small-scale combat, especially single unit combat
Supreme General: Giant dropper and recoverer - You excel in massive-scale combat, and have the smallest recovery costs, and a drop cost discount too
TFC: Versatility above all else - You lack the raw power of the other 2, but make up for this with commands that are useful in any situation, the ability to support others while also boosting yourself, and an army discount that lets you hop from planet to planet with a greatly reduced command bill for doing so.
The Classes:#1. Army of One
Purpose: As the name implies, this allows you to make one extremely powerful unit, at the cost of not boosting anything else, at all. This is by far the easiest of the classes to use well, and also the most straightforward.
Strengths: Ao1s excel at single combat, or squad-based combat where you squad is centered heavily around a particular unit. They're also especially good at using + units.
Weaknesses: Because all of this class' power is put into a single unit, you won't be very good at being in multiple places at once. You're also going to be much weaker in large-scale combat than the other 2 classes.
Unlocking this class: You need Survivalist (which you'll probably want anyway at some point) and Charisma (eww, worst ability in the game). Survivalist makes sense for 1 guy piloting a superunit, but Charisma is an... odd prereq to say the least. I think Frizz just really wants someone to actually use Charisma.
Suggested minimum level and abilities: 50 - Most of this class' abilities further enhance the other commader-specific abilities (Shield Master, Skilled Gunner, etc), which you can get for much cheaper. Additionally, if you're relying that heavily on one unit, you'll want to make sure you can keep it alive with protective commands.
Root skill: The root skill of this class is rather lame. You gain access to hotkeys for 2 of your task forces and ummm... that's it, for 15 LP.
Update: Frizz later changed this class so you can pilot + units without the merit if you have this class.Additional skills:
Defensive Mastery - Commander: +25% Shields / Armor, +1 Gunnery Level Dodge, -1 Damage per hit taken
Offensive Mastery - Commander: +1 Max Speed, +1 to-hit, +1 Damage
Support Mastery - Commander: +2 Controlled Speed, +5% Shield Regen, +1 Acti Charges
Suggested skill order: The order they're listed in is likely best. The defensive boost is just too huge to pass up for the others, and while Support Mastery is certainly useful, Offensive Mastery is more directly useful.
#2. Supreme General
Purpose: This class is all about dropping massive armies, and somewhat reducing the huge expenses of doing so - as well as lowering rebuilding and reviving bills in all types of combat.
Strengths: No one can outdrop an SG, and no one else can auto-recover units without burning mod slots or actually salvaging.
Weaknesses: Although you can drop huge, you get no combat bonuses whatsoever to any of those units. When not in huge-scale combat, you're at a major disadvantage vs. the other 2 classes. You also have to watch out for skilled squads picking off units - no one can actually give orders to 120 units in a turn.
Unlocking this class: Unsurprisingly, you need the 2 regular army limit expansion abilities
Suggested minimum level and abilities: None. With this class, it's less a question of level and abilities, and more a question of whether you actually have the units and crews to support this style of play. If you do, then you're ready. If you don't, then you're not.
Root skill: This class gets by far the most powerful of the root skills. You gain +15 to max army size, hotkey control of all 7 taskforces, 10% autosalvage on absolutely everything, and immunity to overkill on crews.
Additional Skills: The 3 other skills are identical. Each adds another +15 to max army size, and reduces all deployment costs by 3%. The deployment cost reduction DOES add to existing reductions on planets. If you have the full 9% and drop with a 75% discount to attack a supernode, you won't merely take 9% off of what's left, you'll increase the 75% to 84%.
Suggested skill order: Since they do the same thing but cost increasingly more points, not taking them in order would be just plain stupid.
#3. Task Force Commander
Purpose: The task force commander falls somewhere in between the 2 extreme classes, and is a more active class, focusing on gaining commands rather than passive boosts. Unlike with the Ao1's super unit or the SG's enormous army, TFCs favor versatility over raw power. You also get a nice discount to drop costs, helping to mitigate the cost of all of that spam, and making it easier to hop from planet to planet as needed.
Strengths: High versatility paired with the ability to support the other 2 classes with heavy command spam - you have some value in absolutely every situation, even when the forces you have deployed suck.
Weaknesses: Because you lack the strong focus of the other 2 classes, there is no one area that you really dominate.
Unlocking this class: Like SG, this requires the 2 army expansion skills, which IMO, is kinda odd.
Suggested minimum level and abilities: 90+, with all or nearly all of the combat commands learned. A TFC that can't command spam well is just a gimped SG.
Root skill: TFC's root skill isn't quite as huge as SG's, but it's still quite powerful. You gain hotkey access to 4 taskforces, +15 to max army size, and a 10% reduction on drop costs. The deployment cost reduction DOES add to existing reductions on planets. If you drop with a 75% discount to attack a supernode, you won't merely take 10% off of what's left, you'll increase the 75% to 85%.
Additional skills:
Improved Move Out - This upgrades Move Out, causing it to last an extra turn, and granting +2 movement instead of +1.
Improved Aimed Shot - This upgrades Aimed Shot, causing it to give +2 to hit instead of 1.
Improved Power Burst - This upgrades Power Burst, restoring 10 points of shielding twice rather than 5.
Nano Burst - This is a new command, and repairs 5 armor per turn for 2 turns. It's basically a regular power burst, but for armor, and makes it *much* easier than normal to conduct field repairs.
Suggested skill order: I suggest either the order I list them in, or taking IPB before IAS. IMO is useful is just about every kind of battle, as well as drops that aren't battles at all (like scouting for the Zed bacon). IAS is very powerful when you really need it, but it's not something you need often. IPB, on the other hand, is weaker than IAS, but applies to a much wider range of situations and works on allies. It's a tough call as to which of those 2 gets priority. Nano Burst, while certainly useful, simply isn't something you're going to be using all that often. It's a nice added boost, but I wouldn't give priority over the main 3.