Hi, @santi.
Let me start by stating very clearly that I’m not even an intermediate regex user. I’m not being modest, here. It’s just that regex is so powerful that even a beginner can do amazing things.
I started to learn regex out of necessity, while doing some text cleanup that would otherwise be very tiresome. I found it so useful (and so much fun) that I kind of took it as a game I regularly play.
My advice is to start with practical examples; real-world problems, preferably something close to an immediate need of yours. Like finding all e-mail addresses in your vault. Or all dates. Checkout these awesome playgrounds:
They both contain lots of example patterns, they both explain to you what part of the expression is doing what. So just pick one (or both) and go crazy.
VS Code has very robust Regex capabilities (others too, but I prefer this one); opening a file and hitting Cmd+Shift+F will allow you to experiment freely (on your own, though).
This may seem dumb, but only after getting the very basics, I’d go over a tutorial. Rexegg has one of the best.
When you start to feel more confident, you can play Regex Golf, where the goal is to build the smallest possible expression that satisfies some given conditions.
And of course, feel free to ask for help.