Ideally, R50 THM. Though you can just stop at R20.
You would want:
Sacrifice I/II/III for Regen effect
Siphon MP I/II for quick MP recover upon defeating enemies
Blood Rite I/II and Dark Seal I/II to boost damage and accuracy of your spell
Stygian Spike I/II to recover MP via getting hit when grinding
Flashfreeze I/II because it's the only way for Mage to Incapacitate mobs and get certain loots
The rest are optional