Choose two: enchantment, abjuration, and necromancy. For the most part, all three of them are Will save or suck/lose.
If you want reasons for why illusion and conjuration are good, look at the shadow x spells to see why illusion is good (Also your imagination, but that's very player dependent). Conjuration is good by virtue of having so many damned (good) options, from teleport, to no-save-just-lose to summons to....