Okay, today I bought a Mongoose DXR AL (yes, from walmart). Before you say anything, let it be known that I am broke (can someone say college student?), so I cannot afford even an entry level bike from a LBS.

All I want to do with this bike is ride. I am not interested in taking it on any trails or anything. Basically, I just want it to help myself get into shape.

After having ridden it today, I came to the conclusion that the shifters and derailleur SUCKS (of course, you all already knew that). My question is: What would be some good options for upgrading these parts?

As of now, the bike will suffice for level terrain. However, its not quite up to going uphill, of course at this point, neither am I.

Please don't suggest that I go to a LBS, becaus there is no way that I could afford anything from one right now, and I really can't wait until I can afford one because by then I might decide not to get a bike at all (I have several other hobbies at the moment that would quickly tempt me to give them some attention).

Any advice would be great.