I think the best way to learn React Native is to understand what mobile development is. I was coming from Microsoft .Net MVC core/Xamarin , so I had an idea of what building an app was about. What I mean is that I need to know the basic concepts, such as Drawer, Toolbar, TabBar, ViewPager or Button. They are pretty obvious, and I don't think it should take me more than a couple of weeks to get familiar with the components of an Android or iOS app.
React Native is an excellent open source framework, that uses Javascript to let us create without too much effort Android and iOS applications at once. It is reaching right now, in my opinion, a level of maturity high enough to be considered production ready.
In the next level I'll try to enhance the project with JWT to provide Authentication/Authorization services.
