First off, a rifle is a better choice to start with than either a handgun or a shotgun. Shotguns have BIG recoil, and aren't pleasant for most new shooters (or even many long-time shooters).
Most of us would recommend buying a Ruger 10/22 as your first rifle. You can get a new one for $150, and it will teach you a LOT about rifles, shooting, safety, etc. Plus, the fact that you can buy .22LR ammo for $9/550 rounds (WalMart) means that you can practice a lot for very little money.
If you aren't willing to go that route, consider saving up some more money and picking up an AR15. The Group Purchase rifle here is a heck of a deal, ammo is affordable, and an AR15 is a quality weapon that you could use to defend yourself if the need ever arose. It's fun to shoot, has light recoil, excellent sights, excellent accuracy, and more accessories than any other gun that I'm aware of.
With the money you have, you could also go with an AK47 clone. These are fun, and certainly a serious weapon, but no where near as accurate, flexable, or "nice" as an AR15. Ammo and mags are still inexpensive, though, so you could afford to shoot it.
Don't rush your decision, and do lots of reading here...
-Troy