I'm going to add to those who say don't TRY to build a stash. Instead, just buy for the projects you are doing. Over time, you'll probably buy for something you're going to start "right away" and then not get to it- that becomes stash...
My stash seems to grow without me trying. And the stuff I bought in early years to have on hand is still on hand, and not really my style.
The only thing I really like to 'stock' is white.