If you are just starting to build a stash I would buy 1/2 to 1 yard of a lot of things you love. You'll always find a use for them. Bigger pieces of yardage are good for backings and continuous borders but I love have lots of choices for a quilt and don't like going out to buy something to go with. I love having solids or things that read as solids for blending. I love smaller prints and then bigger ones for focus quilting. It just depends on your budget, storage space and desire to be an addict like the rest of us.