here is the best resource for gimp beginner tutorials
http://www.gimp.org/tutorials/
begin with the "Beginner" tutorials and keep going down to "Intermediate" and then go to "expert"
there are further skills on that link i typed but once u reached expert, u can make almost anything if u have enough ambition towards makng it, a word of advice also, dont try to do all in one day, after u learn something new, practice it a while b4 moving on, this is really important as everything has to sink in :P, anyways hope this helps u with ur sig, and no, u dont suck, u should see some of my work [ i sucked] on when i now started out and now,
im an expert web designer
so keep trying, u'll get there eventually