I would save anything any size. Paper piecing and appliqué both require small pieces. If saving cut pieces I would have storage for different sizes 11/2" stripes and squares, 21/2" strip and squares, 31/2" stripes and squares up to 101/2" strip and squares. Plus fat quarters or 1/4 metre lengths of fabric and bolt metre size for backing. I should spend when you can and see fabric you like. You never know when money becomes required for other things.