Rifleman is a class which have hp(aika online gold) amounts and higher defense rating. So you can you can get out of some sticky situations and lets you take more damage than average. You can attack from father range in PVP since it gets you outside AOE range for bosses.
Damage of Rifleman is in single target fights in Aika. So please make your head on straight to make you not loss a single one on fight. Such as you will let a warrior in to close while at half health. That said your only real enemies are warriors. Everything else is a free kill one on one. Just get the first attack in on a warrior and you will always win.
Instead find the softest targets and take those down as fast as you can to give your healers an easier time because you wont be able to AOE things down in parties. Your relatively high defense also enables you to take a bit of a pounding, so parties may use you as an off-tank if things get desperate enough especially since a rifleman can out damage any other class on a single target, so holding agro on that one mob will not be a problem.