If you've noticed, I've mentioned that you need maps to enter some areas, and if you'll look on your character sheet, you'll notice aan Area Maps section and a Starmaps section. Maps and Starmaps cannot be bought, only found off of enemies you have killed. If you have a Steal-type ability, you can even steal maps from other players, but the thing is, it's a very small chance for that to happen, especially since you don't know if they even have a map you need.