I like that text, what is it? That's besides the point though. You really need a lot of work. For starters, that render is pretty bad and you need to make different layers, not all on just one. Other than that the effects are pretty bad. You should take a look through some GIMP tuts to get your skill up.
Well, the background is poor doned, the text is way too big, the render is bad cutted, anything I forget to say?
Basically, all you need to do is find a better render, and use different layers and use a good gradient, and you'll have a good sig in no time. This isn't too bad for your first sig. Just follow a tut, and you'll be fine.