Best full body/ portrait lens for nikon d5100?

I'm 15, i have a nikon d5100 and the standard kit 18-55mm lens. I have photo shoots for fun with the girls. I usually just take up close face shots and some full body pics.price is kinda an object, i don't make to much money, i'm a 15 year old boy so the cheaper is better! What's the best lens for under $500? And also if you are reading this and you have a good portrait lens for sale email me s3an0709@gmail.com.

That's easy to answer - a 50mm prime lens.

There's a 50mm/1.8G and a 50mm/1.4G prime. The latter is slightly better but about twice as expensive. If you are really serious about photography then it may be worth to get the f/1.4 version. Otherwise the f/1.8 one does just fine at half the price.

Be aware that the 50mm primes don't only come in two maximum aperture versions, but also in different versions regarding autofocus. There are old manual ones without autofocus. These are sold used e.g. On ebay or craigslist and named "Ai" or even "non-Ai" You don't want any of these. They won't autofocus of course, and won't meter either on your camera.

There are AF ones, which typically also have D in their name. E. G. "50mm/1.8D AF". These would meter on your camera, but they won't autofocus as they don't have an autofocus motor in the lens, and your camera depends on the lens to supply the autofocus motor as it doesn't have one in the camera body. You most likely won't want one of these either.

What you will be best off with are the ones that have an autofocus motor in the lens. Those have AF-S in their name, and typically also G. E. G. "50mm/1.8G AF-S"

You might also consider a 60mm f/2.8G AF-S micro nikkor. That's a macro lens. It's very nice for portraits, except that it does not allow you as extremely shallow depth of field as the 50mm primes (albeit f/2, 8 already is very nice), it's not as low light capable, but you get full macro capability on top of the use as a portrait lens.

Be aware that all suggested lenses are prime lenses, they don't zoom at all but use a fixed zoom setting at the given focal length.

No such thing as a best lens. The kit lens is already great for what you're asking for. To take more flattering shots (the ones with very cheesy backgrounds) get a fast 35mm lens. The f/1.8 is very good for its price but if you have more cash, the lower the f/number, the better.