Before diving into React or Phoenix, take a step back and survey the state of the Web APIs. From hardware and device access, to client side storage, web of things, gpu compute, and high performance peer nets. There are infinite possibilities to combine different technologies into new innovations. And new additions arriving almost daily to become inspired by, such as SharedArrayBuffers and Atomics.
My advice is to find a topic you genuinely enjoy that is much in demand, perhaps web payments or security, and really gain some mastery in that area. Blog about your progress, publish articles and tutorials and of course build things! Then you will be on your way to becoming an authority and the go-to person for advice.
Two good blogs to get started are Mozilla Hacks and HTML5Rocks:
My advice is to find a topic you genuinely enjoy that is much in demand, perhaps web payments or security, and really gain some mastery in that area. Blog about your progress, publish articles and tutorials and of course build things! Then you will be on your way to becoming an authority and the go-to person for advice.
Two good blogs to get started are Mozilla Hacks and HTML5Rocks:
https://hacks.mozilla.org/
https://www.html5rocks.com/
Good Luck!