First of all, welcome to the forum. You will find that this a great place.
Second, Winchester makes good and cheap practice ammo under their USA brand also known as Winchester White Box. It can be found at most Wal-Mart stores in 100 round value packs.
Remington also has a "discount" brand called UMC and it comes in a yellow box and can be found in 250 round value boxes at some Wal-Marts and larger sproting good stores. Remington also sells this ammo in "normal" boxes of 50 rounds in a white and green box.
I hope this helps.