Yes, use GIMP, it's very good. Contrary to popular belief you do not need Photoshop to create the best signatures, GIMP is fully capable of producing some impressive results if you take the time to learn the program and all of its features. It's always a shame when I see people diss GIMP and tell people they need
Photoshop, it's just not true. Not to say Photoshop isn't better, it is, but it's not a must-have. GIMP will serve you well! Then just look up some easy beginner tutorials to learn the basics and slowly move up in the complexity. Skills from GIMP tend to translate well into Photoshop too, and vice versa, which is why starting with GIMP, whether you intend to eventually get Photoshop or not, is a good move.
Another good thing you should try if you want to get more serious is get some peer recognition. Feedback is the BEST thing to get! Get your friends to critique or join a forum that will. A friend saying "That's awesome!" won't exactly help you grow though, you need actual critique and constructive criticism, which means negatives
. Friends tend not to like giving negative feedback but it helps a lot. ZD doesn't have one but what helped me on an old Zelda forum was a Graphics Thread where you post a new signature and you need to give good feedback to 2 people above you. Not just "thats awesome, love the colours!" but actual
feedback. With some thick skin you can take the bad and improve upon it. A graphics thread will suffice, but I liked the community of the old OGFX Thread.
A thread to your own doesn't create that I think.
Though if you do want Photoshop, go download the 30-day trial of it and when it runs out re-install your OS and download the trial again. Simple, and you'll have the fastest computer ever! No viruses! I did that for years
until I actually got it free from Uni, to the point where I kept the .exe files on an external HDD for easy access.