What do you intend to use for bedding when they are done in the brooder? If you will continue to use shavings, buy a bale of shavings. If you plan to use a natural or DL bedding, you can buy what ever makes most sense to you. You will pay almost as much for a bag of shavings as you will for a bale, and the bale will go much much much further. You change or top off the litter as often as it needs to be done. If you can keep them from spilling water, the shavings will stay dryer. (elevate it above the level of the shavings after the first day. Aim to have it as high as the chick's backs when they are standing up. When I brood chicks, I simply top off the old shavings with a fresh layer every couple of days. I also hang their waterer from a chain. It makes it super easy to adjust the height as they grow so quickly.