Store them in zipper baggies so they won’t dry out before you use them. I’ve found the quality rub ons stay pliable and easy to transfer to my projects if I store them this way.
Another idea illustrated here is to go ahead and rub them onto small pieces of paper which you can later use as embellishments. You can make them dimensional with foam behind them, ink the edges, color with blending markers or colored pencils. Really the options are truly endless.
The best part is you don’t waste any of your beautiful rub ons!