A little about myself

I'm Ady, i've been writing a novel and i'm trying to draw an atlas for the world in my novel. So, after looking into the tutorials on here i decided to become a Cartographer and try my hand at drawing it.

I'm 23 years old, from snowy England. What is the rule of thumb when it comes to drawing a world. The quandry for me is my world in my head is 5x the size of Earth.

Software I Have
GIMP
InkScape

Style of Map I'm aiming for
my novel is about pirates but so far I have tried my best to not have cliches in my book. Since is harder then it seems.

If anyone can help me draw a large scale map then i'll be grateful

Ady