I almost exclusively learned the basics of Elixir / Phoenix by looking at the source code of https://changelog.com which is at https://github.com/thechangelog/changelog.com.

Major kudos to them for open sourcing their platform. It covers like 50+ common web dev features.

I pretty much skimmed the docs to get the ultra basics, looked at that source while I was building my own app and then asked questions when I got really stuck. Even managed to sneak in some refactoring on their code base a few days into learning Elixir. It's super approachable without much more if you have some type of programming background beforehand.