The standard aproach is 6x120 Mage/Med/Eval/Resist/Necro/SS with a Mage Weapon.
Theres also a very viable Defensive Wrestle Necro/Mage template that uses lots of skill increase items. The pro to it being you can't be Disarmed and still have defense when using Slayer spellbooks, and the con being item dependancy. It can use Aegis Of Grace, Bloodwood Spirit, skill Scrapper's or spellbook, skill ring or Crystalline. The result to aim for is usually 120 Mage, 120 Eval, 120 Resist, 120 SS, 105 Necro, 100 Anatomy and whatevers left in Med (usually 80+).
Theres other things you could do like Scribe/Necro/Mage or Mystic/Necro/Mage also. They're all pretty good.