Alright, so without giving newbie unfriendly optimizing advice:

Take a few of each kind of spell. One damaging spell, one spell to hinder the enemies and one to help your allies.

I do recommend both Fireball and Lightning Bolt. Fireball occurs beyond the range of your allies, usually, and can soften the enemies for them. Lightning Bolt starts at you and hits in a line. So you can reach out and touch someone reliably even if they're standing left or right of your allies.

Enervation is good, but if you're getting into the mess that is Metamagic, you can use Draining instead, which you can apply to Magic Missile, so you get up to five hits instead of Enervation's one. Or apply it to Fireball and hit several enemies at once right off the bat and let your allies mop up.

Yes, the tank might be doing 35 or more damage to as many foes as Fireball at 10, but only if they all sit in the exact right place and wait for him. You can hit them without charging out to them and then getting beaten on. And do it while he's wasting time charging at them.