There is this common trait that people believe that they must go out and get the best, most complicated tool that is available and then torture themselves in learning it.
The best advice I can give you is to use the right tool for the job and do as much as possible with as little as is required.
Yes, there is a vast gap in capability between GIMP and PS but you, right now, are not within that realm of requiring that capability.
I started out with Paint Shop Pro 7 and used it until I had come to such keen knowledge of it that I was clearly aware I had finally surpassed its capability and upgraded to PSP10.
Don’t think of what PS _could_ do until such a time that you know that GIMP is no longer enough. Concern yourself with the actual art making rather than the flashiness of your tools. An artist picks and changes his tool according to what suits his subject best, rather than using the sledgehammer for all tasks.