just write
just write
How writers write, get started writing, re-write, re-edit, complete manuscripts, and overcome writing obstacles vary with each person, situation, and deadline.
In my opinion I'd say yes to all of the above you asked here: yes, continue character development, work on the plots, write treatments, and write outlines.
Which should you start drafting first?
Pick one, any one.
There's really no right or wrong answer.
Writing is an exploratory process; it takes real commitment with the simple activity of writing things down on paper or typing into a word processor on your computer or laptop, (or mobile phone, if you're writing while you're waiting on line at the super market).
In time you'll eventually find out what "your" writing process is.
Finding out about other writers' writing processes will definitely help, inspire, and motivate. As much as possible keep doing things that will keep you inspired and keep you motivated.
But realize there comes a time that, well, you've just got to start writing - inspired or not inspired - and whether you think you might have a couple or "many" short cuts handy or in your writing arsenal, there's really no short cut to hard work. Write things down, re-write, re-edit, don't be afraid to throw drafts away and re-start. Just write.
Select any of the things you listed above and as you write and as you explore let us know how choosing to begin there helped and had its advantages and disadvantages.
*