Skelemancer:
Pump skills into raise skeleton at beginning levels, then once you get to act 2 put a few into skeleton mastery, and switch back and forth
Also put one into amp to double your skeletal damage, and when you get to nm act2 you should buy a might merc.
For stats, focus on Vit and energy with enough dex to have at least the same block rate as your sheild. A class can live in nm with only 250-300 life, with good block rate

It will be tempting to max out vit, but make sure to keep in touch with your str so when you find a better armor, you will be able to put it on.
I also have corpse explosion at level 2 for my mancer, because i was finding it's a lot faster killing in baal runs (a lot faster) and you barely use any mana raising skeletons once every 20 mins
Also, skeletons raise in life with each difficulty, my skeletons have 750+life in hell, and they do 200 base damage (amp+might = a lot more damage)
Skeletal mages are a waste it seems, and revives are your choice (but i would go CE instead if i were you)