I rarely buy fat quarters, but when you need 16 of them for one project...it might be cheaper than buying 1 yard of more fabrics. Can you use your fabric for as many as you can and then just buy some fats to fill in?
Also - if I am using my own fabric I just cut what I need from the end of the fabric and not make fats out of it. Many times they just want a piece or two cut from each fabric...not even using the whole FQ.