I haven't actually Played an occultist yet, but I've been planning one this last week...
Illusion at mid-levels will grant you Shadow Beast, for some decent summons that don't stop at early spell levels. Unfortunately, Conjuration's servitors quickly lose relevance.
Transmutation has Quickness, which is why you'll probably want it at early levels. Being able to touch an ally with a haste spell at level 5 gives you a solid buff for your group's fighter at the same time a wizard would normally get it. With a touch more added defense, at that.
Abjuration as one of your first implements is also useful for providing a Shield to a two-handed (or two-weapon) melee character.
It's not my flavor, but I'm sure many will argue for the Necromancy. Needing only a coin as your implement, and the ability to make a long-lasting servant, will probably serve you well.
As for spells...judge for yourself. Abjuration will likely be taken early for the sole purpose of grabbing Shield for yourself, for some tankiness w/ a bonus to con and Mind Barrier. Conjuration lets you become the team healer, but I recommend it early. Else, its servitors quickly become useless for anything combat related. Transmutation's liberating command is a good one too.