My list, core spells only. Alot of concurrance with Lord Z. Some quibble.
4th Level:
1) Evards Black Tentacles
2) Enervation
3) Stone Skin - Defense is more important than offense.
4) Minor Globe of Invulnerability - Defense is more important than offense.
5) Dimension Door - Defense is...
6) Improved Invisiblity - Are we noticing a pattern here?
7) Polymorph Self - The multipurpose spell. Can't get buy without it.
8) Polymorph Other - 'You are a trout.'
9) Lesser Geas - Never underestimate the power of an expedient cohort.
10) Scrying - Knowledge is power.
If I had to change something it would probably be Enervation for Wall of Ice or Phatasmal Killer. Note the overall lack of direct damage dealers. By this level, you've usually got better things to do with your spells. At some point soon you are going to need Dimensional Anchor, but it probably can wait.
5th Level:
1) Wall of Force - One of the games most essential spells. Wall off hazards until you are able to deal with them.
3) Prying Eyes
3) Hold Monster - Duh.
4) Dominate Person - Duh.
5) Telekinisis - A must have general purpose spell. When throwing things, is one of the better direct damage spells, because its attack is indirect and thus bypasses SR and energy resistance.
6) Summon Monster V - Ahh.. finally, the summoning spell you've been waiting for: Celestial Dire Lion, Giant Eagle, whole flights of Lantern Archons or Varguoilles, whole packs of Dire Weasels. And at last, the spell duration is long enough to justify the expense.
7) Cone of Cold - If you feel you must do direct damage over a large area. Sweeps areas clear of weak monsters, and doesn't do alot of collatteral damage.
8) Teleport - Another must have spell.
9) Passwall
10) Mind Fog
Mind Fog could be traded out for Animate Dead, Permanancy, Fabricate, Persistant Image, Major Creation, Wall of Stone or some other general utility spell if you don't find charming foes, sneaking around, and so forth is really your style. Cone of Cold and indeed any direct damage is arguably unnecessary, and also could go in exchange for one of the above. Transmute Rock to Mud is alot of fun if you think you can fit it in.