I buy 3 yds if the fabric is nice to be focal fabric for border and squares. Others I buy 1-2 yds depending on price/sale. I try not to buy without pattern in mind/hand so that I do not have a large stash of facrics that not go with anything. also I try not to buy backing. binding or sashing fabric until the squares or top is done due to I then decide what color/pattern will look nice with the finished top. I have changed my mind often so I now have unused facric that matches nothing at this time. I can not aford to have too much stash.