In the under $50 category I would totally recommend getting a sidewinder.
It looks so nice! It has programmable macro keys and backlit keys. It also has anti-ghosting technology, where you can press up to 26 keys simultaneously without ghosting. Pretty cool. It feels nice to the touch and the action is great. Seriously looks cool though, especially in the dark... it like glows deep red.
The gaming keyboard you can afford is above, the gaming keyboard you WANT is below.
Mine is $47 at a local computer store!
I'm getting it with my new desktop.
Look around a few websites you can find deals sometimes. Newegg one time got my Logitech G15 for 35$ on sale
I would suggest one of the logitech keyboards
There are not a ton of great options in the under $50 category. If you can manage $65, you could get this awesome logitech keyboard.
Custom color backlit keys, programmable g keys, game mode switching, and generally sleek aesthetics are some cool features that come with this thing that you might not find in the under $50 category.
Very nice stuff from logitech.
I got one of these and it served me well for a long time. at 30$ it was very affordable, and came with a lot of features (light up keys, extra programmable dials + buttons, etc) and had a very high quality feel. Keys light up blue through the characters on each key.