I started with Gimp, years ago. The thing with Gimp is that it's so easy to use, the interface is completely user friendly and it's fun to do things on it. But the problem is that whether you like it or not, you will be forced to go to Photoshop. And everything you learned from Gimp will have to be re-learned, so maybe... 5% of all the techniques, concepts, ideas, skills i learned from Gimp are still relevant now that i'm on Photoshop.
You might think Gimp is great but eventually you'll realise that it can't do things you need it to do and you'll feel like Gimp is just weighing you down because of how restricted you are - you'll realise just how restricted you have been when you jump onto Photoshop.
My suggestion to you is to just to take the leap of faith and get Photoshop, follow tutorials and just do it over and over, only doing them to get effects you like. Ignore anything you haven't learned unless you see it used in a tutorial otherwise you might get overwhelmed by the amount of options in the program.
I saw the message you sent me on Youtube and i realise you need a background but at the moment i'm really busy so, when i have some spare time, i'll contact you and make sure i get you a decent background.
~Andre
HD | GFX