It is strongly encouraged that you create a submission for any world you roleplay on which doesn't exist in canon or as a submission. Otherwise you may be asked to submit the planet if you wished to continue roleplaying on it.
If the planet is only in your character's background and not a world you're roleplaying on then there's no need. I as well as plenty of others have made vague mention of worlds that are not actually on the map just for story reasons.
Hope that helps!
So I'm making a character, which would currently be this one I am posting as. I want her to be *the* leader of that planet. I can just make it up as a place to put her and then if it becomes a more necessary planet, I could then create a planet of my own? In other words, nothing would have to be done right away in creating my own world?