A very interesting thing about Dialogflow CX is that it is similar enough to ES that many concepts are borrowed, but different enough that you need to learn it in a different way.
So here are my tips for learning Dialogflow CX:
Learn the building blocks of Dialogflow ES first
If you have no understanding of how Dialogflow ES works, you are probably going to waste quite a lot of time learning CX. The simplest way to learn the building blocks of Dialogflow (IMBO)  is my Step by Step guide to Dialogflow.
Understand what a state machine is
As the documentation says, CX is a state machine based approach to building conversational agents. And I start this course by first explaining what a state machine is.
Build a very simple state machine based bot
I have created an example of such a bot in the Dialogflow CX Beta course. In this course, you will build the Vendee Bot, which is a very simple example of a state machine bot.
Ignore all the complex terminology when you begin
There is quite a lot of stuff that isn’t necessary when you start, such as scope and state handlers. And they actually get in the way of learning. So don’t start there.
Incrementally learn and understand the complex stuff
But remember one thing: if your bot is actually very simple, you would be better off just building it in Dialogflow ES. 🙂
Ultimately, the point is to learn the complex stuff too.
In fact, that’s basically what a Google developer advocate told me in a tweet. So you DO need to understand the more complex stuff later.
 In My Biased Opinion 🙂