Since you can draw, the software doesn't really much matter - it is just a tool. Pretty much any basic paint program (gimp included) can do what you want, especially if you have a tablet - once you learn the software. Otherwise, as Azelor suggests, just scan in hand drawn work and post process/composite/colourize it in that program, but again, learning the software and how to use it is the key...

Also, when you want "realistic looking maps" do you mean something that looks like it was made historically, or something that done with ink and quill, or a more isometric/painterly map, or realistic in terms of the paper/parchment/weathering/grungy look? And "same kind of map as everone else on the forum" is a bit broad, as there are a tremendous number of styles used here. Just flip through the Cartographers' Guild - Finished Maps Thumbnails - L to get an idea of the variety....

-Rob A>