Welcome to the Guild Akarius! Well there is quite a bit you can do with GIMP alone (though having a vector program such as Inkscape is also really useful). Several members, including myself, work primarily with this software. There are also quite a few tutorials here written for GIMP (just check the tutorials section, and also checkout the "Tutorials in PDF format" sticky in that forum). So that's one hurdle down. Once you've explored some tutorials and are ready to begin, post up a WIP map page and ask for feedback. That way you can pick up new tips and tricks and make course adjustments to your map early on. Look forward to seeing you around.