If I find a fabric I can't live without I usually buy 4 yards (or more depending on quilt size I plan to make)to make sure I have enough border/binding fabric and also incorporate the border fabric into the quilt. Once I have a pattern, then buy the other coordinating fabrics for the quilt. I always buy more than what a pattern calls for because we all make cutting mistakes(lesson learned) and you can always make a string or scrappy quilt from left over fabrics. Better to have too much than not enough.