Its been awhile since I've played diablo, just got back into it but still struggling to learn what is best for each class. Specifically the best gear affixes needed for each class and why

That’s a lot of info to provide in a post.
It literally can not be covered without knowing at least things like build, playstyle, content.

So I’m going to say life, and when all else fails stat.

Check out Maxroll or Mobalytics

check mobaltics tier list