I've got 2 feeders. One is pretty big and holds about 20 lbs. The other is much smaller and hold about 5. I get the big bags at Costco in the winter which contain some combination of Milo, Cracked Corn, White Millet and Black Oil Sunflower seed.
I don't fill them up as much in the summer as I do in the winter. Its pretty cool to watch a day or two before a snow storm how the birds all flock to the feeders and clean them out. How do it know?
I get a pretty decent assortment. Mostly wrens, finches, doves a few orioles, cardinals and the occasional blue jay. Theres a chipmunk or two that live under my deck that make regular visits as well.