Hey, this may be a little late, but here are a couple tutorial videos to begin with:
Here are some great sites that give examples and show you how to use different syntaxes:
https://skripthub.net/
https://skunity.com/
http://en.njol.ch/projects/skript
https://skriptlang.github.io/Skript/index.html
And if you are looking up how to do something specific or you have any problems such as your custom skript not working, there are plenty of youtube videos and threads online where you can find what you are looking for.
Good luck!