some people build their stash with nothing but fq's and charm packs; some people buy 2 yards of everything...it all depends on you. what kind of quilter are you? do you do alot of pre-cut's quilting? do you do alot of turning twenty types with fq's? do you make big blocks? it is a personal thing what you work with and everyone is different.
for me, if i love it and think i will use alot of it i buy a lot of it. if i like it but do not know what i will ever do with it i may only buy a fq...if i'm working on something in particular and know what i need i buy at least an extra 1/2-1 yard just to be on the safe side and to add to my stash.