1. Wisdom, of course
2. Magic (preferably all 4, but 2 will suffice: Earth (resurrection, portal to the city, explosion) and Air (door and flight))
3. Intelligence (mana)
4. Logistics and Pathfinding (you always run out of moves)
5. Diplomacy
6. Attack and Defense (it has never hurt anyone, and especially not mages who struggle with this)
Without points 1-4, it's always difficult; 5-6 for good measure, and you can do without the rest.
And some skills just make you want to spit. Especially when there's nothing to choose from.