One work around for using your kit lens, is to up the ISO, keep it as wide of an aperture as possible. Anticipate the players motions as best you can. When someone spots up for a shot, take your shot on the ball release. There will be less motion at the height of a jump for a layup, dunk, rebound, etc. You will still be extremely limited though and you will still only wind up with a few keepers probably. The best investment money wise would probably be the 50mm 1.8 someone recommended. I shot highschool volleyball with my 70-200 2.8 and even that required an ISO of 1600 wide open and I had to stay zoomed out to 70 ( and still felt a bit too close all the way at the back of the bleachers.) So 50mm should be a perfect focal length, and if you shoot it at f/2 ISO 800, you should do alright, or even 1600 for some extra speed. Just make sure your exposures are spot on.