The first app teaches you to find users before you build the second app. Take a look at a book called "Traction: How Any Startup Can Achieve Explosive Customer

The first app teaches you to find users before you build the second app. Take a look at a book called "Traction: How Any Startup Can Achieve Explosive Customer Growth" by DuckDuckGo's founder Gabriel Weinberg. He goes into various channels on how to get users and improve the product.