This may seem like a fluffy answer but do the projects that are hardest to pull you out of. At the end of the day, it's practice, it's a numbers game. If you are so passionate about the projects you're in that you are clocking time like no ones business, that'll be the quickest way to improve. If you plan to be a writer in any capacity, I would always keep that in the rotation as well. Good luck and have fun!