I will be a bit of harsh here, you must have design documents for such project.
To clarify design documents are not drawigs, well should have some drawings, but not kind you think about right now.
You need to describe in detail game mechanics, how you connect to server, your business model (maintaining server is not cheap, so you need to have some income).
Then some decisions if you go for kickstarter, or get loan in bank, or seek some investors. You need money for trips to game dev conferences to advertise your game.
Maybe you apply for Epics grants to promising developers, etc. You need to plan all that stuff before you start developing game.