If you want the binding to match an included fabric, be sure to save enough fabric with the top. It will store better uncut. Backing? Well, prices are only going to go up, so if you have something appropriate just make sure you have ENOUGH!
I had the "perfect" batting set aside, but the long-arm quilter I hired wanted a wider margin around the quilt than I had calculated, and I had to either buy something I liked a lot less (on sale) or pay more than I wanted to spend (full price).