I'd recommend
https://start.microprofile.io/. Pick MP 4.0, OpenLiberty as runtime, and include samples for all APIs. That'll get you a demo project which you can run right out of the box, and source code you can study to see how the different pieces fit together.
That's how I got started when I felt should take the plunge, and it's really easy to get started with. Of course, you can pick some other runtime; I just happened to use OpenLiberty and was happy with it.
Also check out the
OpenLiberty blog where you'll find lots of useful information on other features of OpenLiberty (it is a full
JEE server, after all), and how to push MP APIs further.