If I can afford it, I buy at least 3 yards for my stash (4 yards if I am afraid that the store won't have it later on). If I can't afford that much, I try to buy at least 2 yards for my stash. When I started folding my material like bolts and storing them on shelves, I found that almost all of my stash worked well together with each other. That gave me more confidence in being able to just buy something because it is pretty and knowing that I will use it later on in different quilts.