Do you need an outline?
Well, you have a couple of options. You could begin writing, right now, or you could start with an outline.
This is a question writers always argue over. What works for one person won't work for everyone. So no, I can't give you a yes or no answer to the outline question. I can only give you three questions to ask yourself.
If you outline more, and stick to your outline, writing your book will be a much faster process. If you want to spend the time playing in your story world, and falling in love with it, you’ll take more time, but possibly have more fun.
Always write when you feel the inspiration to. Don't force yourself to sit down and write an outline when you have a scene in your head. And if a story you're writing turns out more complicated than originally planned, you can always pause to make an outline anywhere in the writing process.
Trust your instincts, and remember your two golden rules. Read, read, read, and write, write, write!