12345QEZXCG, M3/M4/M5 are all keys I use with shift/alt/ctrl modifers as it suits comfort. RFVT are all also good, I just use them for general purpose stuff like focus target, inventory, and mini-map. I use Ctrl+Spacebar for Limit Break on most jobs, Shift+Spacebar for target's target.

Play around with what's comfortable to reach with your fingers. Anything menu-based near your movement keys should be put somewhere else to give you more workable keys in combat.