[binaryapparatus]

I did initial plunge into Haskell when I started using xmonad, looking at config file was visibly 'something else'. I would probably recommend starting with Haskell first -- if you want to properly blow your mind that's the way to go. All the principles are common so diving into Elixir took very little time afterwards. Some principles are getting their way into imperative languages and it is much easier to grasp them on pure functional level first. Understanding and using map, filter and reduce, in JS project, was much easier to grasp immediately because they borrow that logic from functional languages.

Elixir is beautiful but probably few notches easier to understand and write than Haskell. Reason I would start with Haskell is that it doesn't hide functional logic with syntactic sugar. For example variables in Elixir are not mutable but since you can assign to the variable already used in function, it can prevent programmer from understanding what immutable really means.