I am by no means an expert, but what I know I've learnt by doing. I'd like to think of myself as a hands-on user and I think that experimenting and practising via meaningful examples is the only way to go. Online tutorials constitute a major source of help. Personally, I have not attended any paid courses (yet). I got all the info from free tutorials. I had had some experience with Python programming and Unity before I took up learning Godot which made it all a breeze. Godot has an intuitive way of handling (most) things, thus being user-friendly.
Usually it is best to start a project and see it through. That way you get to learn multiple aspects of the engine while having fun doing something that intrigues you. This is the project-based approach. Think of a game that you would like to make and start learning how to accomplish each step along the way. For example, if you want to make a 2D platformer, you will learn all about vectors, movement, position, sprites, collisions, hitboxes and even animation in the engine.
Although I have not worked on anything serious, I have set up multiple mini projects, each with their own goal and purpose. I have even created a Test Project where I create a different scene for each little experiment that I want to try. I have scenes to test shaders, mechanics, maths algorithms, animations and more. In fact, everytime I decide to answer a technical question here on this forum, I first set up a new scene and try out my solution before I recommend it. I have accumulated quite a few such scenes.
The key is to start simple. Make new scenes in Godot and create small bits of code. Start with simple movement controllers and collision events. After a while you will have a library of ready-to-use assets for any project. Why create the same 3D movement control anew when you've already made it once. Don't reinvent the wheel. Oh, and make sure to name everything using informative names so that you can find what you are looking for any time.
Another method of practising is to take part in game jams. Get involved! Even if you don't make it to the submission deadline, you will still have whipped up something, you will still have learnt something in the process.
If all else fails, online forums will assist you. Any question that can't be answered via simple googling can easily be answered in forums. Don't be afraid to ask for help.