Joker or Chord (Who to pick on the Selector)

I know a lot of people would be saying Chord but I guess this is just me asking, is Joker still a relevant unit? I played on launch, didn't get him and quit the game for some time lol, came back for the anniv!

How necessary are the 'elements' in the game? I'm not aiming for meta right now since my account is probably just 3 months old, I am still in Akashi's Palace/story and am taking my time. I just like beating most content but I know my expectations as a new account and currently F2P.

I already have Makoto, Hatsune Miku, Frostgale Mont and Yukari from this anniv~ I mostly use them and the 4stars like Closer(electric). I don't really have a 'Curse' unit still. Is Ren a good pick or should I just continue building Sepia and Rin? Joker was crazy good in 1.0 but I'm really clueless about him now.

THANK U