Figure out a monthly budget and put aside an amount for your quilting then put the cash in an envelope marked "quilting" then when you shop use that money only to shop with. One month you may not use it all. Keep it in the envelope and add to it each month. Example: January $20- spent $15, Feb. add $20-spent $10, March add $20 you now have $35 in the envelope to spend. Your not going over your monthly budget but you have a little bit put aside for a bigger expense when it comes along. Just don't spend more than is in the envelope. If you shop on line put that amount of cash back into your checking account.
Another thing to remember is the tradition in quilting was: Use what you have available.