This guy can help you out. If this video doesn't point you somewhere, maybe a binge-watch will. Though, from the standards of a regular writer who talks to girls and people in general, his ideas on certain notions of chracterization (*See Great Player: How to be a Female, or whatever it's called) can be a tad weird and antiquated, (I'd take some of his specific character advice with a grain of salt, but his character-building advice is good) but from a storytelling/game design standpoint, what he says in most of his videos is pretty much on fleek.
The best RP characters are characters that fit in their world, and the best worlds are worlds that make some sort of sense. Try to flesh things out, and always build up before you build out. Like sandwiches, syrup, shields, and so many other less edible things, plots are best when they're thick.
