I recommend Gimp, and spend your money on a Wacom tablet. The Bamboo Fun is a good model for the casual artist--it probably has the best price-to-functionality ratio available right now.

CC3 itself costs only $45. The add-ons and supplements, though, can push the price up rapidly. The entire collection from PF costs over $600 if you buy it all at once, but you wouldn't need most of that stuff. I'd say CC3 and one of the Annuals would be plenty for what you're looking at doing. And really, you could possibly get away with skipping the Annual, depending on what you want to do. For instance, this map: http://www.bryanray.name/maps/vendria.jpg was done with CC3 alone, with the exception of two textures I borrowed from here and the line drawings.

Anyway, welcome!