- I would suggest make a small app with just basic crud operations. It should have a front-end, backend and a database and then work incrementally to the other steps mentioned below.

- Use k8s to deploy and run your app.

- Add more business logic where you will be needing more tools like elasticsearch, message-queues, etc.

Some examples from the top of my head are Stock Ticker app, Ticketing software like Zendesk, Food delivery App, etc.

Note: Start small, add one feature at a time.