Recommendations would also depend somewhat on the player's role and focus in the game. If OP (original poster) is really into crafting, then Gatherer might be appropriate. If OP likes the new Pet Battles, there are AddOns to help with that.
Honestly I think WoW is a very easy game to pick up and play (especially compared to Vanilla WoW so many years ago). You can get by - in fact MORE than get by - with no AddOns. We have a Death Knight friend who has raided quite successfully and is an amazingly good player with zero AddOns. Default WoW UI has come a long way, but still some ways to go.
As others have pointed out, AddOns exist to solve a problem. If OP has a problem with something in WoW that a UI adjustment or alert would help, chances are there is an AddOn that will fix it.
Possibly the most BASIC UI element that is STILL missing in WoW is the ability to move parts of your UI (user interface) around. With that in mind, I'll just leave this suggestion here:
MoveAnything
Enjoy!
-T.