I started building my stash way back in the early 1980s when we didn't have jelly rolls, etc. (which only came about in the very late 1990s/early 2000s), and I did it by buying 3/4 yd. of fabrics that would 'go with' other fabrics.....also called blenders.
I still do this; in some cases I buy 1/2 yard, in others 1 or more yards. But I rarely buy big yardage of one design for the stash unless I'm considering it specifically as a neutal background or backings (this 'neutral' can be pastels, ecrus, tiny prints, 'sky-type' fabrics, etc.).
Having this sort of stash, and trying to work mostly from it when I find a larger print or a fabric to die for, encourages me to learn to how to build a quilt from 1.) my own stash without buying a collection for a quilt; and 2.) makes me work with colors in ways I might not be exposed to if I were to purchase all the go-withs for a specific print or pattern I see.
It pushes my creativity. It makes me build quilts with many colors, not necessarily scrappy quilts, as I see how different reds, or blues, or greens, work together. I feel my quilts are richer looking for this method.
Now, after nearly 30 years, I have a stash with probably 4000-5000 different colors/prints in it, though some are less than 1/3 yard, or even a fat quarter. I raid my "random pieces" storage boxes regularly when pulling fabrics for a quilt.
I'm always surprised when I read about those who buy several yards, or even a bolt, of a specific fabric. I don't feel like I'd ever want to work with a large amount of any one fabric over and over again in several quilts.
Isn't it wonderful that there are as many different ways of working as there are quilters doing the work?!! :D
Jan in VA