Have no fear. Creating good-looking maps is something that can be learned. I am by no means a master, but the difference in quality between my first map and my most recent ones is tremendous, and most of that improvement has been thanks to the tutorials and advice available here.
So post up your works in progress (WIP) as soon as you can--the earlier other people start looking at them, the faster they'll improve.
Welcome to the Guild, and enjoy your time with us!