Put the word out to parents of the school that you are looking for donations of early reader books. Lots of times their kids have outgrown books and parents are happy to donate. Contact local children's libraries and let them know your situation. They also often get donations they can't use. Meantime scour thrift stores for "just right" books for your kids. If anyone money comes available, start building your "just right" library. It took me a couple years to build my library, then some wonderful parents who were teachers came in and leveled my free books! Awesome. If money is really tight and all you have are basals to use w/guided reading, work with what you have and gradually build your class library. I mostly collected books that could be leveled, but I also found great books at adult levels on eagles, wolves, Grand Canyon, etc. The kids love to look through these grown up books with the great pictures.