Start with a user journey
A first release needs a clear beginning, middle, and outcome. Write down who the product is for, what they are trying to accomplish, and the single journey that gets them there. This gives you a more useful scope than a long list of disconnected features.
Separate essential from interesting
For every feature, ask whether the first user can finish that journey without it. Authentication may be essential for private data. A complex reporting suite may be able to wait. Keep a visible list of later ideas so removing them from the first release does not mean losing them.
Define what you want to learn
Decide what evidence would justify the next investment. That could be people completing onboarding, coming back to a core workflow, or choosing a paid plan. Instrument that journey before launch and pair the numbers with conversations.
Plan the handover early
Agree where the code lives, who owns service accounts, and how the application is deployed. A useful MVP is something your team can run and improve after the first delivery, with documentation that explains the important decisions.