Just start at a level you [i]are[/i] comfortable with and keep challenging yourself. Join a Free or Casual roleplay and push yourself out of your comfort zone a little bit with every post you make. Create a character you think is cool and think to yourself [i]how can I make them weaker, more flawed, more interesting?[/i] Write a post and when you're done, add another paragraph to spice it up, even if it's just to describe what your character is seeing, hearing and feeling. 

Continue this for five years and you'll be fine. :sun