Actually you can make some headway without getting any database involved:
- Get started with Elixir via Elixir for Programmers (PragDave) - Phoenix is used without getting a database involved.
- Functional Web Development with Elixir, OTP, and Phoenix (Pragprog) builds an even larger Phoenix application - again without a database.
The advantage to this approach is that you get first introduced to using the “Phoenix is not your application” way before exploring “Phoenix is your application” - which is more like many RoR web applications are built.