This has been a very interesting thread. I think a stash builds itself, at least mine did. I got the quilting fever in 2004; started off buying 1/4 yard pieces. That didn't last long. I still only buy 1 yard pieces; but, that's because of finaancial issues. I only buy on sale, unless I'm buying from my local QS; never find fabrics on sale there. However, I don't use only QSQ, though I don't use thin or see-thru. Oh, my stash was increased greatly when I inherited my mother's large stash. Took me months to give away all her double knit; I still find a piece here or there, lol.
My advice is similar to the previous posts. Buy at least a yard when on sale; mostly blenders and tonals. and have fun!