As far as I know, most players spend all 30 points into Intelligence. You may want to spend a few points in piety so you're at 244 piety at level 50, however. The only reason to do so is solely for AoE reasons. When you have a scholar in your party and you use convert. at 244 piety you have exactly enough MP to cast another fire II and another flare. Any less you can cast a fire II, but no flare.

This is simply preferences, though.