here is the best resource for gimp beginner 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