Playing as a rifleman is one of the best feeling in the world for me because this is actually the first class I chose when I started playing Atlantica Online. I know it was nerfed heavily, but it is still fun nonetheless. It is classic and the attacking pattern is pretty convenient.
My strategy is quite cheesy, but I'm sure it works. All you need is Valkyrie, Spartacus, and Lich. Once you have the mercs, just let gun main be gun main lol.
Attack buffs: 459%