If it helps, the duvet cover you want is about 2.3 times as big as the pattern. Other things being equal, I would buy 2.5 times as much of each fabric and look forward to the leftovers. (Actually *I* wouldn't do that. I would make a spreadsheet, figure out exactly how much of each fabric I needed, obsess about the accuracy of my figures and the fabric selection, then either find it in my stash or buy way too much anyway, changing my mind about the layout, the fabrics, the pattern, and everything else several times while sewing.)