I have lots of stash, but never the right colors to complete, so always seem to "need" one more perfect color to go with. As far as amounts, it depends on the fabric- 3 yards, fat quarters and yd pieces are usually what I purchase.Then the horse panels well that is another story!
I have recently been doing 30's Fabrics in a Farmers Wife Sampler so keep an eye out for them now, and that's usually fat quarters.