My advice is not to try to build a stash. It will grow with every quilt you make. Go to consignment and thrift stores and check out the clothes, not as clothes but as fabric. You will be amazed at the beautiful patterns that are available. Just stay away from polyesters and knits. You might also like to check out a few of the big name quilters that specialize in reusing fabrics, Bonnie Hunter is the one I can think of right now, I am sure there are others.