@Neo and Zekai
I'm giving Neo's character Jessica, Raylin, and Katrix's new character Dorm Number 106 A of the female dorms. Have fun~! Oh and I'm working on a post for TSU right now.
A nimble, close ranged powerhouse with potent long ranged capabilities as well, Gunner makes for an excellent solo class. The Twin Mechgun's weapon action has the Gunner perform a side or backflip during which the player is completely invulnerable yet still able to attack. Many PAs involve positional kicks and dives with something for every occasion.
Chain Trigger marks a target much like Weak Bullet, but does not take effect right away. The Gunner's party can build the displayed chain up anywhere from 1 to 100 hits, which will make subsequent attacks stronger once it is activated when struck by one of the Gunner's PAs. Other party members cannot activate someone else's CT, but their own PAs will count towards the chain combo. Also unlike WB, only the Gunner's immediate party can see or interact with the CT, not anybody else in the MPA, and only the Gunner themself will get the damage boost.
Sustainable DPS Build:
The idea is to stack a lot of general damage boosts that are always active while regening PP during the SRoll that you should be using to start every PA to double your damage. But note that SRoll Up/Arts themselves do not get any bonus from JA, so these should not be used for damage purposes, only PP regen (for which SRA is counter productive).
Without ever switching from the Twin Mechguns, this build still has a lot of utility and damage, either at close range or from a distance, to a single target or many, and is not obligated to hit weak points as their only form of damage. Of course, with everything at once you can see some insane numbers, and it's easier to achieve than when subbing Ranger.
Burst Damage Build:
Its ace in the hole is the deadly WB+CT combo for achieving incredible maximum damage on a single target on a cooldown. That doesn't mean you can neglect the other three WBs in your rifle, as simply going AFK between each shot could still add up to more total damage than your own little party trick.
Your general TMG (or even rifle) damage doesn't suffer too much of a drop compared to the /Hu builds, albeit with a much higher reliance on weak points, though you should always be looking for an opportunity to use your Chain Trigger. And not to a 100 hit combo, either. About 20 or 30 hits gives you the greatest bonus per hit, and any more can actually end up being less damage over time, even if you don't miss the Chain Finish which is entirely likely.
The extra points in SRoll Up and SRArts are mainly for building up your Chain and doing respectable damage doing it, since neither will set off the Finish. They can also boost your general damage since you can shoot before getting your SRoll JA.
Ranger is a high damage potential, mid to long range class with several support options. The support is mostly trumped by the high damage options that Ranger has under the right conditions, especially since many enemies have Ranged-specific weak spots (the head). Weak Bullet (WB) alone makes Ranger a desirable class, since it not only turns any one point on a target into a weak spot for Ranger's own passive damage multipliers, but it also grants everyone triple damage on the target which stacks with whatever regular weakness the enemy already had.
While rifles are the obvious boss killers since they're tied to WB, launchers and gunslashes are your AoE trash mob cleanup tools. You'll want to carry all three to maximize your damage potential in every situation, with a Hunter sub for the best damage multipliers available.
Pure DPS Build:
Maximizing damage on your Ranged attacks, with frequent usage of Weak Bullet to further boost your and your party's damage by 3x. I can't stress this enough, but Weak Bullet is the best support in the game, allowing everyone multiple chances to deal vastly increased damage that stacks with any and all skills and effects (except more WB, that only refreshes the effect, maximum one per enemy at a time).
Killing Bonus doesn't directly increase your damage, but it can be surprisingly helpful at times. That said, each point isn't significant, since it's only 1 PP per kill, so you could choose to max Weak Hit Blast Bonus, First Hit, or Trap Search with your spare SP along with however much from KB as necessary.
Weak Hit Blast Bonus is fairly minor since Rangers should be getting a full PB gauge quick enough already, not to mention the PB itself is not helpful enough to be using regularly.
First Hit doesn't boost every hit in a multi-hit PA, so only a launcher could get much use out of it for mobbing. Against bosses, even if you do get the first hit, WB actually deals a bit of damage on its own, so First Hit will never stack.
Trap Search is for relief from a common annoyance and not so much extra damage or anything. If the other skills don't catch your heart, we finally have enough SP to justify taking this skill (along with Just Reversal if you can't fit it on your subclass).