Chronocrypto here with a small but powerful tool, lets you easily design beautiful apps, program powerful functionality with easy drag & drop, then upload your apps to the Google Play Store and App Store. Now do this a couple of times and you have your own google play store app store mini store.

Thunkable X

"Thunkable ✕ is a cross-platform app builder that enables anyone to build their own native mobile apps."

Pros: Love the amazing design capabilities, you can live test the app before you launch it.
Cons: This takes some time to understand.

"Examples of apps built using the DIY platform which the team flags up to include a dice throwing app (called Dice), built by two teenagers from Oregon which has gained more than 500,000 downloads on the Google " Would you not like to build an app and have it downloaded and used like the Dice game above. Imagine the ad revenue.