Some kind of progressive playground ?
Well, as you asked about web applications… I know no better playground than the one you get with mix phx.new playground --no-ecto,
I’d start with it to build a simple Hello World page with a picture of choice .. (--no-ecto to skip database and its dependencies) … then play around with more features.
As with foreign languages, you learn a lot more syntax and words by actually using the lang you want to learn… even if nobody understands you at the beginning 
(here the elixir compiler will be carefully listening to you)
So don’t waste too much time looking for resources, build something, you’ll have plenty of specific questions to search for then (an infinite stream of…). Have fun.
