It is your choice on how you quilt. Me, sometimes I am inspired by a fabric, other times by a pattern. I have bought kits and made them and I have some waiting for me.
I will buy a kit when I love the fabrics used and it would cost me far more money to buy small pieces of many fabrics or it is just so well coordinated. I bought a fantastic kit to make a quilt using a panel for my grandson. It has such generous cuts of each fabric, that I will have enough to make him a pillow too.
This year money is especially tight and I an thankful for my stash.