I recommend getting both, Photoshop is more automated while Gimp has more options.
Also, Velve.
Ahem.
THAT SIG SUX. DD:
Sorry, it's true, you need a lot more practice. I wouldn't post a sig like that even if it was my first time, seriously. :P Gimp can do a lot of stuff, and can be easy. Try it out. Good luck. :>