I have done it both ways, but it is frustrating to me when i see a line of fabric that i "have" to have, but i don't have a pattern in mind. i don't know how much to buy and tend to overbuy(if there is such a thing). i can usually find one eventually. sometimes i see a fabric and a pattern jumps into my mind. Just starting out, it's easier to find a pattern first and then pick out the fabric. when you become more familiar with more patterns, it will be easier to buy fabric first.