mainly, str for dmg(it is atk/elemental based mainly)
int for SP/recovery(helps asura dmg too)
and dex for cast speed+hit(FINGER OFFENSIVE CAN MISS-although this would mainly apply to pvp and MvPs since you should have enough dex to hit what you are training at.)
remember theres a stat and skill resetter for a measly 1000 zeny, so experiment with the numbers(if you have dex gears remember to use those)