I have a NikonD3100 but want
I have a nikon D3100 and i love it! But then again i hate it. I look at other pictures from photographers and i feel like their pictures are more crisp. I want that! But i don't know what kind of lens to get. I'm on a very low budget so can't afford a $500 lens i need something with a decent price but great quality?
Any suggestions? Maybe upgrade camera?
Don't even think about an upgrade - if you can't afford a decent lens, you can't afford an upgrade either!
There's nothing wrong with the quality of the D3100 - not in the right hands (ie someone who knows something about photography.
You need to know about metering & photographic exposure, lighting and composition - when you've mastered that with the lens you've got, then will be the time to think about adding to your lens collection.
Don't blame the tools - blame your lack of skill.
The D3100 is a great camera, but it won't take the pictures for you. A professional can take a cheap point and shoot and still get good results out of it. So at very least look up some photography tutorials. As your knowledge grows and your skill improves, your pictures will get much better.
You don't need a lens, you need this book:
When you talk about "crispness" do you mean "sharpness"?
It may be a simple matter of remembering that once you edit your digital image you need to sharpen it as the last stage of the editing process. Have you realised this?