I just finished the game with a pure wizard.
Metamagic Feats: Empower, Quicken, Extend Spell
I actually used only Empower. For Fireball, Flame Arrow and Cone of Cold. I had Boots of Speed 'til the end, thus no need for quickened Haste.
Spell Focus: Necromancy, Evocation, Enchantment, Conjuration. See Spells used.
Other Feats: Combat Casting
Skills: Concentration, Lore, Persuade, Spellcraft
Spells used:
1
Summon Monster I(!) - upgrade
Sleep - drop later
Mage Armor
Magic Missile
2
Summon Monster II - upgrade
Blindness/Deafness - drop maybe later
Endurance
Bull's Strength
Invisibility
See Invisibility (seldom)
Fox's Cunning (because it did stack with Int+ items)
3
Summon Monster III - upgrade
Fireball
Hold Person - upgrade
Haste
Flame Arrow - for higher levels
4
Summon Monster IV - upgrade
Improved Invisibility
Minor Breach (name?) - upgrade
Stoneskin
Confusion
5
Cone of Cold
Hold Monster
Summon Monster V - upgrade
6
Binding Call - upgrade maybe
Greater Breach (name?)
Greater Stoneskin
Circle of Death - maybe drop later
(Mass Haste was not that useful, because me and my henchmen were permanently hasted)
7
Finger of Death
Delayed Blast Fireball
8
Greater Binding Call
Horrid Wilting
9
Wail of the Banshee
Timestop
I really had no need to use other spells, sorry.
My tactic was to summon a Dire Creature or Celestial and let him fight alongside my henchmen. I could stay in the back and cast some spells to take Bosses out.
In retrospect, a sorcerer would be another valid choice. You could cast much more spells before having to rest. And featwise, thats OK, too.