Scrappy is just that.....Scrappy without much thought or consideration to the usual rules of selection.
I got a jelly roll in a swap and made a tube quilt. I sorted by light/dark or light/medium so there would be some contrast. A little by color but not toally. Even put some fabrics in that I would not otherwise use such as letters and pictures.....It worked great. I believe the success is not obsessing over it too much. Toss the fabric down and shuffle them up and bit and then go for it.