and
https://elixirschool.com/en/lessons/basics/basics/
And while I haven't watched it - there's a free code camp tutorial - https://www.youtube.com/watch?v=IiIgm_yaoOA
From looking around there seems to be a host of free videos on YT as well as many books on elixir/phoenix. Also, I believe prag studio gives away 1/2 of that initial course for free, probably enough to get you started.