Camera settings for a cheer competition?

I'm using a Nikon D3100 and I have a kit 18-55mm lens and another 50mm 1.8G lens.
Which lens is more suitable and what settings should I use?
Normally I set the shutter speed to 1/200 with aperture 1.8 and ISO 3200, the picture is still too dark. )

It must be really dark where you are shooting. I can shoot inside arenas at f2.8, 1/500 and ISO 3200.In your situation all you can do is keep raising your ISO. This is totally a lighting issue and no camera is going to change the situation. You have a fast lens and if you shoot it at f1.8 you are at a very wide opening. I also think you need to up your speed a little unless you are shooting only when the people are fairly still. 1/200 is too slow to stop action. The more I think about it the more surprised I'm at how dark it is where you are shooting. Just raise the ISO and good luck. You can get a program like "noise ninja" to help you reduce the noise in the shots. And yes, the 50mm is the lens to use, the other lens requires 4 to 8 times more light depending on what mm you are shooting it.