Just here to show you a cool series on YouTube that some people might find useful. It's not made by me - it's created by a guy called Brackeys, who also made the Inventory System on this topic. He's made some nice tutorials in the past but this might be one of his most in-depth tutorials, and I definitely recommend you go check it out.
Here's the first episode:
Personally I've found some parts of the tutorial quite interesting, especially since there's a new multiplayer backend, and a new API which is a little bit easier to use