Is your DM allowing you the standard wealth for an 8th level character, and letting you buy magic items?
If yes, then I'd strongly advise against spending valuable spell slots on anything that's still useful when cast from an inexpensive 1st level wand. (which basically means anything with a duration of 10 minutes/level and up)
For 2nd level spells, let me throw in another vote for Glitterdust. One of the best spells in the game.
Fireball and Haste are good 3rd level picks - Haste is an absolute must for parties that aren't caster-heavy, and still great for any party. Fireball is sort of meh and a bit overrated, especially if your party already does a lot of damage, but still useful, and hard to go wrong with.
Finally, for 4th level - I'm a little surprised (or maybe I missed it?) that no one mentioned Enervation yet. It's powerful, has no save, doesn't actually have the Evil descriptor, and it's the perfect spell for a spontaneous caster that can use it repeatedly.