Relevant expansions. New to wow besides classic. I have a 60 warrior and some other toons on there. But I decided to try retail and I enjoy it alot. I leveled a warrior to 40, then bought the newest expansion and then tried a bunch of different lvl 110 toons to feel out the endgame. 

I tried druid out and loved it so much I decided to use a 110 boost on it. I've progressed a decent bit in kul Tiran, and am lvl 113 atm.

Problem is, I'm worried that I'm missing important content from previous expansions i know nothing about.

Do I need to go back and do anything from any other xpac? 
Or is none of that relevant since BFA has significantly better stuff.  I've heard about artifact stuff and whatnot and I'm not sure if stuff like that is important.