I think it depends on if you are planning on using Imoen or not. If so, take all the skills that she doesn't have, especially Pick Pockets and Set Trap. If you have good Pick Pockets skill you can recharge wands free which will help a lot when you dual to Mage. (Obviously pick pocket the wands back BEFORE you dual.
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In my opinion a Bounty Hunter or Assassin would be a good match for a Mage. No one in the game can lay traps and traps ROCK! Assassin/Mage looks like the ultimate anti-mage weapon... Breach -> Poison Weapon -> Melf's Minute Meteors 8-)
Pick Pockets is way better than Hide In Shadows: you can always steal more Invisibility Potions.
Obviously if you're not taking another thief along with you (Yoshimo, Jan or Imoen) you need to have Find/Remove Traps at 80-90 pts. Open Locks is very good too, though there's a Mage spell which will help. Just decide if you're going to ditch Imoen though... in my opinion not an option for a good PC.