You want a nice smooth flow to your zipper, so I tend to like coil by the yard and then I order zipper pulls to go with how many yards. . I base that on the average length of my usage, which is 12 to 17 inches. Base on that I will order 3-4 zipper pulls per yard. You will also need zippers for your linings too, those would be a smaller finer zipper. When starting out try to keep your experimental cost down.