Keep in mind you can always reset your specialization with this quest.
Just need a ruby.
http://wiki.project1999.com/Respecialization
IIRC, Spec 200 should result in a 10 percent reduction in mana usage for what type you go with (e.g. Alteration spell costing 200 mana should cost 190). Spec 50... 2.5 percent?