I have a middle-sized Really Useful Box for my buttons. Inside it, they are bagged by colour. Press studs and hooks get another bag, eyelets another, and frog fastenings another. The lid is starting to strain, yet I never have the right buttons for a job. Fortunately, I can nip into Brum easily enough to stock up on goodies from the market...and there are plenty of suppliers online too.
I dodged buttons for years as none of my machines ever made a nice buttonhole...but now I have my vibtage Singer one, happiness is ever at hand!