What camera lens should i be using?

I have a nikon d3100 i'm not used to slr cameras, i'm only 15 and i love taking pictures of my friends at the rink and at shows, its hard to get pictures of them doing jumps and spins with the lens that comes with the camera if i don't have a tripod and its not easy where i live to get around the rink with a tripod and find a place to put it i need a lens that i would be able to get the picture WITHOUT a tripod
if you should tell me the name of a lens and maybe a site i could buy it at that would be great

Increase ISO starting form 800 going up. Set to Aperture Priority and set to lowest f/number. Try shooting. Increase ISO until you eliminate blur. You will have to compromise with picture grain as you increase ISO so it would be critical to know when to press the button. Don't use LiveView, use the optical viewfinder. It would help if you knew exactly what to expect so you'll have the image in your mind as it happens then fire.

Don't worry if your lens isn't long enough. Just shoot at maximum megapixels and crop the pictures later in the computer to make them appear you were closer or had a longer lens. It doesn't have to be close to be that dramatic all the time.

They sell poll tripods, there just long sticks that mount to your camera so it isn't so shaky, you should look into those. I've seen a guy use it ( And his pictures turned out wonderful, I saw them) I might get one…

I highly recommend you get a monopod. Even with fast lenses it can be nice to have a monopod to support your camera and it hardly takes up any space compared to a tripod. A good lens for quick sports photography would be the Sigma 70-200 for Nikon. It is cheaper than Nikon's 70-200 but still an excellent lens. If that is too much maybe look at a Nikon 70-300 which will be much cheaper but won't work great handheld in low light.

Basically if you want a fast lens, it's going to be expensive and VR will not fix your problems if action is involved.