All depends about the mechanicals of the server:
- Renewal dmg calculation
- Using a custom version for dmg
If he's using a renewal version for dmg, gx is all about dual weapons according the needs and cross impact spam if I'm not wrong.
If is using a custom version for dmg[assume that is just adding the skills and make them working more or less nice according the info in the description of the skill] probably the best is using % stuff for more dmg with the usual sinx builds for dmg: high str, dex for hit, vit to survive but not enough to be raped by a thana, agi+dex for max aspd, bla bla bla.
It also depends a bit about if thana cards are easy or not to get and how custom is the server.