What's your budget?
I am looking to get a speedlight mostly for the basketball seasons, and i just need one in general. I have no idea what to look for in a light, so i turn to you guys. I am using the D3100 if that makes a difference.
If you are going to shoot basketball games in a Gym and you are allowed to use flash then you will need something with kick. As Eduard says look for a referb SB600 or SB800. You can also go with Anthony's suggestion and go manuel with a LumoPro LP160. The only lens you list in your profile is a 70-300mm f/3.5-5.6. Without flash that lens will be to slow and won't give you enough shutter speed for stop action shots. Even using it with flash you will get a shadow cast from the front edge of the lens without using a flash bracket. For basketball I would suggest using a Nikkor 50mm D, f1.8. It's not very expensive. If you can get on the sidelines that lens will give all the close up shots you want. The D3100 will give excellent performance at higher ISO levels. So the 50mm at f1.8 at a high ISO should give you enough shutter speed for stop action you can live with without the flash.
Unfortunately Nikon did not put an auto focus drive in the camera. If it had you could have used the D lenses that are less expensive. The 35mm AFG f/1.8 will work fine you just won't have the advantage of a little longer 50mm lens. You should still get good actions with the 35mm. You will just have to wait for the action to come a little closer.
If you can't take flash shots at the basketball games are you still looking at getting a flash?
there.I would recommend using an 18% gray card to set the white balance at the gym. Any further WB correction can be done in post processing.
The Nikon SB600 is in your price range, but for a bit more, you could upgrade to the SB700 (about $329). I use the LumoPro LP160, which rivals the SB900 in function at less than half the price.
Honestly, I don't know why people use anything else. For $160, you get a $400 flash unit that is built by photographers, for photographers. It's 100% manual, so it doesn't have TTL function (which is why it's so cheap). If you're the auto-pilot type, stick with TTL flash units. But if you want the most bang for your buck, get the LP160.