Basically $$$ = sharpness with a lens. Spend your money here, but make sure this is something you for sure want to learn/invest in.
You bought a good entry-level DSLR. See if you want to spend the time to learn how to operate the camera, before you start investing. You really won't lose much on glass though.....the loss will be in the body itself, but that also depends on what body you have. I bought my first DSLR quite a while ago. I self-taught myself how to use it.......I cut the camera on manual and figured out how to expose shots, never looked back. Once I got some shots that I thought were decent, I started posting on the Canon forums (POTN) and asking for feedback. There I learned how to prioritize different settings to capture different things. For example, learning low light shots need a tripod/low ISO and a balance of a long exposure to the correct aperture.
The biggest thing to learn though, at least first, is how each setting affects another.......between exposure, aperture, and ISO. A good rule of thumb to start with, is knowing you ideally want to shoot with the lowest ISO possible.