I only started to really feel I was moving to another level with React when I was given a large UI project to tackle and told we had to use React & Redux and bring as much of the code under unit tests as possible. After getting through that and producing something I could feel I truly understood, that's when I felt I could call myself a "React graduate".
Based on this, my advice would be:
- develop an idea for a product you'd love to create, ensuring it's complex enough to keep you busy, but within a reasonable scope (i.e. doable within a month or two)
- perhaps your workplace can assist your learning: ask about sizeable projects coming up that you might take on with React (or consider your options if your workplace isn't willing to help you on your learning journey)
- keep up to date with brainy folks who write about their React findings & advice, Medium is great for this! Find a few articles about React that you like and start following those authors and their publications; you'll start getting pretty regular, relevant articles in your inbox daily after following a few of these
Above all, put your learnings to work and build things, solve problems, and have fun! :)