Buy the best walking foot for your machine. You won't regret the cost but you will regret the wasted money buying a low quality one. The low quality generic ones I have used will not feed evenly, are flimsy and break. Look on Ebay or at online sewing machine parts shops.
This book is just for quilting with a walking foot. It's the best I've found: One Line at a Time by Charoltte Warr Andersen[h=3][/h]