There is no better teaching tool than composing. Go ahead and write something and you'll find that you start to have specific questions that you can research and then apply what you've learned. If you wait to get started until you know everything you need to know, you'll never start, because there is always more to learn. You'll write good orchestral pieces after you've written a lot of bad ones first as practice, not after you've read all the books.
Just start. And share, so you can get useful feedback. But get rid of any expectations of it being good. That's a great way to make yourself too fearful to write or to share. Just write, and keep writing.