good ole' wally world tends to have cheap ball ammo. At walmart I have purchased 100 round boxes of 9mm, .40 and .45 ACP from winchester for a decent price. I have also purchased 250 round "mega packs" of UMC (which is remington ammo), and 250&500 round boxes of american eagle for a good price. the most recent box I got my hands on was American Eagle .45 ACP - 230gr target ammo. Shoots a little dirty, but, not bad... especially for the price. I mean, if you're going out and plinking, you're probably going to clean your gun when you get home anyway right? I picked up that 250 round box for like $90... which is a really good deal for brass cased, target ammo. Sportsmans warehouse, Bass Pro, gandermountain.com, midwayusa.com, have all been places I have purchased from..
Good luck buddy! let me know how it works out for ya! buying in bulk is more spendy, but you generally save a little...