I'd suggest spending at least few hours with Vanilla, just to learn the basics.
Starting again at Beginner/Easy in X shouldn't feel like a waste, since the most tedious part of beginnings is smoothed out.

That's the general advice, even base game is complex enough that it's hard to recommend anything, without knowing more about your expectations.
If you're coming from X3, you'll probably be ready to jump right into Xavorion.

Btw.
It's great news, that Xavorion has been recommended as a mod to try.
Thank you, even if you decide it's not worth your time.

Amazing, thanks a lot for your reply!

I'm about to start with vanilla to get used to the controls, hud, etc. but definitely looking forward to try Xavorion.

Cheers!