Costco visitor here. Those 48 x AA packs for about $9 or $10 are great!
I attempted to standardize batteries a while back but gave up. I try to keep lots of AA (alkaline + lithium), AAA (alkaline + lithium), and 123-sized cells (lithium) on hand.
You're also gonna need a way to keep batteries together and protected. Here are a few web sites with cases and whatnot:
http://www.inanycase.comhttp://www.tadgear.comhttp://www.countycomm.comhttp://www.toolsaviation.com