Although it is common to use nail polish to paint, for nail art is very advisable to use acrylic paints.
Acrylic paints are water based which allows you to do a good job with them. They are easy to remove and correct, and the price is lower than the enamels.
To use it you just have to start with a completely dry enamel base on your nail. Start making your design with acrylic paint. If it doesn't turn out as ou expected, remove it with water and you'll have your nail with the nail polish on it completely clean. It is therefore very important that once you have finished all your design you seal it with a coat of clear polish or top coat. If you used enamel for drawing and go wrong, you could just fix with enamel remover, so that you would lose the basis of color.
What colors do I need?
Start investing in a black and white. These two colors are the ones you will be using the most in your designs. With Klein blue, magenta red and yellow you will be able to create all the colors you want. In addition, for special designs you can invest in metallic colors like gold and silver. If you want to buy more colors to avoid having to find the quantities and mix, of course you can and you will save yourself a lot of time!
Where to find them?
In any craft store are available as those are the paintings that use children in their crafts. Any water-based paint should work.
You can also find them in online stores or ebay. I got 18 colors of 10ml between 11-12 dollars on ebay.
Here comes a demonstration!