There are at least 3 main ways to monetize apps that i recommend the most. By the way i would mainly cover the ones that doesn’t impply the sell of a physical good. And focus on apps that commerce with digital goods.
Monetize apps by in app purchases, selling it directly, with Ad networks. Best ways to make money with apps specially if you have 0 budget,
Definitely if you are planning to sell physical goods Stripe is the best option for your app.
It’s so important that you make a Youtube Channel and create videos to let the people know what your app is about.
There are millions of apps the market is saturated, so you need to boost your project with some strategic marketing and best SEO practices.
Also paying for some Google Ads, or paying an influencer, or even better becoming an influencer is crucial to the success of your app. Google uses link building with quality backlinks to score the apps in the Playstore.
In conclusion work every waking hour as Elon Musk stayed to make your app business a reality.