I am always on the look out for stash fabrics that I like to include in my quilts. I am always drawn to polka dots, so ususally buy great looking ones when I find them. Around 1 1/2 yards. Enough to add some to a quilt, and maybe a small border, or binding. I do think it may be easier to start with a pattern that has fabric requirements, and then look for those. It may be less overwhelming.
I also keep a look out for "good" colors that I like. For instance.... a "good" red in my opinioin. There are so many reds (or greens, or blacks, or blues) but when I see one that fits my criteria, then I buy it.
It will take a while, but you will find your own shoppin style! Good luck!