I have been using ScriptRunner for Jira for many years but I never bothered to learn it properly. I don't even know groovy well, but I guess for doing Jira Administration you just need to know about programming and don't need to be a full fledged developer. So I started learning it properly and I thought of also sharing whatever I was learning and it might help others who are trying to learn ScriptRunner for Jira for doing wonderful things with their Jira instance.
Here is the link to my ScriptRunner for Jira playlist.
I recommend starting from the beginning. If you are a beginner and let me know if it was useful.
Enjoy and have fun.