Win Value Pak, Win White Box, RWS (Wal-Mart) Rem Value Pak, Blazer, Magtech and Federal are commonly available and the least expensive range ammo.
If you don't like steel cases , be careful with S&B; their cheapest is usually brass plated steel. You cannot tell the difference without a magnet.
I prefer brass. I can reload it, the gun was designed around a brass cartridge, brass is 'softer' when considering the impact on the extracter claw and mag lips. I know, many shoot it with no apparent problems. It's just been my preference for the approx. 25- 30K through my 75B. I recently had an extracter claw snap off and replaced it. Maybe steel cases wouldn't have changed a thing. YMMV.