O Elixir School é bem legal! Depois de passar por ele, recomendo os materiais abaixo:

https://www.udemy.com/course/elixir-e-phoenix-do-zero/

https://www.udemy.com/course/the-complete-elixir-and-phoenix-bootcamp-and-tutorial/

https://pragprog.com/categories/elixir-phoenix-and-otp/

Abs.!