For your journey1 you will need three notebooks2. It does not matter if you use physical notebooks or digital ones, or a mix. The most important thing is to use them. The notebooks are not a matter for assessment or evaluation. If you do them well, they will be a sound basis for all of the writing that you do along the way. They will help you with your writing.
And, if interested in the history of Apple, Regis McKenna's notebooks are a good illustration of the purpose they can serve over time.