Depends on spells...
Really good ones are (IMHO) Quicken (for later, if you don't want any other), Empower (False Life, Ray of Enfeeblement, Scorching Ray, Fireball, etc) and Maximize (as before, tho I prefer Empower myself). Energy Affinity (MiniHB new version of Energy Substitution) is also pretty good, if you use enough spells with energy damage.
For a Sorcerer Silent Spell and Heighten Spell are very useful, too.
Bye
Thanee