For practice- try WalMart. You should be able to find Federal Champion 180gr for about $12-15/box (50). Winchester and Blazer also offer quality inexpensive rounds. Some like Remington UMC, not my preference though.
Defense Ammo- I like Hornady 180gr. Fed HS, Win Ranger, and Speer Gold Dot are also good options. Others prefer the 135-140gr CorBon loads, which perform a lot like a .357sig round.