In this page you'll know a recommended build for Rangers in Phantasy Star Online 2 who want to focus mainly on their damage. To be exact, you'll see here a pure dps ranger build in Phantasy Star Online 2.
The DPS Ranger Build
The idea here is to maximize all your ranged attacks. A ranger is deadly in long distance combat so its best to prioritize on maxing those great ranged skills. Weak Bullet is one of those ranged attack that you should prioritize as not only that it can boost your damage, but also the parties' damage as well up to 3x more. In fact, it is considered as the best support skill in the game as it allows everyone to have multiple chances of dealing 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).
In most cases, Killing Bonus isn't really that helpful to a Ranger. It may serve ts purpose in certain occasions but you don't use it regularly. Each point it gives isn't that much (it only gives you 1 PP per kill) and it's a good idea to invest your spare SP on Weak Hit Blast Bonus, First Hit, or Trap Search.
However, take note that Weak Hit Blast Bonus is fairly minor since Rangers can full a PB gauge quickly and, PB itself will not be use often in battles.
Also, do remember that 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. This maybe a good option to invest your remaining SP(along with Just Reversal if you can't fit it on your subclass).
The Hunter tree is purely as supplementary damage and not for any of Hunter's weapons outside of dashing or fun times.