A little bit is okay to accentuate your best features or conceal those that you don't find your strongest points. Really, I prefer minimal or none at all. Most women have a fairly decent package without painting yourself up like some type of 3rd grade art canvas! :D
Use makeup to enhance your looks, not to create your looks, as this is where it all goes wrong, a little goes a long way, but young girls need even less as they already have most of the color makeup enhances, so a little will look a lot for young girls.