The biggest mistake I made in buying fabric, was buying too many great focus prints and not nearly enough of the quieter, more boring (think tone on tones, small nondescript prints or marbles) that I needed to co-ordinate with my wonderful prints. I also did not buy nearly enough lights as I didn't realize how important those would be. I needed to be more experienced to realize that you just couldn't mix all those great intense fabrics in one quilt without having the other. Now the most of a great print that I would buy is 2 or 3 metres if I'm making a large quilt. If I find great sales on the boring ones, I'd buy 4 or 5 metres of a great colour that I know will co-ordinate with much of the stuff I have.