None - I did secondary schools with my first wizard which was a Life one, since that I have decided my future wizards can do just fine second school free, so I pretty much have a pure Death and Storm wizard though the game. I only get the blades offered by Niles in Krock Land and then the Sun spells in Celestia, last one in Zafaria. I only consider any other school spells that enhance your primary school spells which I will be eventually getting all my power pips for.
Life to heal others is a waste of time, every wizard gets a sprite spell at a low level, I pack at least one in all my wizards decks, I never depend on another wizard to keep me going. If you must heal others become a life wizard or get treasure cards for that.