A prototype will not get you an investor, to be honest. This is just a fallacy.

If you can fund the prototype, launch it in the market, get some traction from users. See if your mobile app resonates with your users. You need to track whether your app is able to retain those users so that they keep coming back to it.

If you have a good amount of retention with the first few set of users (100 or 1,000), that's a good pitch to take to an investor.

Investors are not looking at ideas, they're looking at businesses that can get, retain and engage a customer.