I second (or third?) the suggestion about taking Energy Substitution as soon as possible. While the Acid Orb is nice, I'd take Electric Orb (or any other) and sub Acid just for the flexibility. Then there's things like Acid substituted in Fireball, Ice Storm, Lightning Bolt, etc. Only take an Acid spell when you have no other similar spell to learn, like Melf's Acid Arrow.
If you DO go Wizard, make your PC a specialist to get the extra spell and the learning bonus.
Sorcerer, while having less spells known and a slightly slower progression, at least allows you to substitute Acid on the fly.
Multiclassing early with a Cleric will open up other spells to such a PC, assuming the right Domains are chosen, and you follow up with Mystic Theurge so you can advance as both an arcane and divine spellcaster simultaneously. As I recall, the Air, Fire, Sun, and Water domains all contain spells that arcane spellcasters can't use that would still be usable with Energy Substitution.
But..uh...don't forget the obvious: take lots of levels in Alchemy so you can make your own, non-magical acid grenades.
Which reminds me...might an Artificer be a good choice? I'm not 100% up to speed on the class, but from what I understand, their infusions work pretty much like spells, and you can have a bunch of stuff prepped for use- possibly in unusual forms.