Welcome to the forums Charity!
Indoor sports are kind of expensive in terms of equipment. There are a lot of cheap telezooms available, but none of those offer the light transmission you need/want for indoors sports.
The cheapest "fast" (meaning it lets in a lot of light) telezoom I'd recommend for indoor sports is the Sigma 70-200 F/2.8. Depending on how far away you are from the court, you might want a 50-150 lens instead, though.
Those lenses still cost around 800$ though, leaving pretty much no budget for the money, and a "general purpose" and landscape lens (you can combine those two).
Fortunately, there's a cheaper option which lets in a lot of light: a prime lens (which can't zoom). Especially a 50mm F/1.8 lens is very cheap (100-200 dollars), but has as a disadvantage that you can't zoom in or out, and it doesn't have a lot of reach. Again, lack of reach depends on the sports venue. Assuming it's not professional, you can often get quite close.
That 50mm prime lens is also great for performances, provided you can get close enough. It lets in an amazing amount of light compared to a standard zoom, which is what you want because music venues/stages are very poorly lit.
I'm a Nikon user, so I'd recommend the D5100 + 18-55 VR lens + 50mm F/1.8 AF-S version (not the AF-D).
I take pictures so quickly, my highschool was "Continuous High".