I've been re-arranging and changing my room since I was 10

In the last 9 years, I've used and abused my walls with sharpies, moving posters, frames and furniture multiple times a year.

I've finally decided to settle down with a set up, and re-paint my room but I don't know what colour. I've had my mind set on a medium shade of grey and maybe a mix of some green or yellow on separate walls.

Here's my problem(s):
I get bored very easily
I'm picky
Most of my newly purchased Ikea furniture is wood (in different shades) - don't remind me
There's only one window in my room
My room is small but serves for a lounging/entertainment area, office, and snake room

Any help would be greatly appreciated

BTW : Does anybody know how to paint over sharpies?
I'm completely new to painting and need to know good brands/types of paints/what kind of primer to use