Don't toss those old brushes and bottles of polish!!
You can also save the bottles and make/mix your own custom colors. Use loose glitter or even loose eyeshadow with some clear polish to make your own glitter polish.
You can cut up the brushes to make different size brushes for your nail art to fit your needs. The brushes pictured I have already cut. I use the black one as my detail brush for nail art (my most used brush) and the Sinful bottle I cleaned out and cut the brush just a little thinner and use as my striper. I use the empty bottle to store it in after I clean and dry it so it doesn't get damaged while I'm not using it.