I buy on sale only. Try to buy only fabrics that will go with anything, like my favorite color in small prints.
Backing fabric and neutrals on sale are the best to stock up on.
Batiks on sale are great for my stash as they all go togather no matter the color.
Charms I always buy at least 3 amd only on sale. Fats always 2.
I only make lap size quilts so yardage is usually only 1 yd.
I have found that quilt shop fabrics are much richer in color than Joanns and they do not match.