What are you most nervous about?
Let’s prototype that.
Think about the whole project and what might go wrong. Imagine you’re six months in the future, what didn’t work?
When there are dozens of things to prototype, focusing on nervousness and uncertainty is the best first step.
There’s no use in prototyping something that’s known. You need to spend your limited energy and resources prototyping to answer the most critical questions.
Trust your gut, feel the nerves and test away!