How would i go about starting up again? I haven't played since auction house days. Any tips on what class to play if I decide to? I have reaper of souls, but I think there's a new xpac?

No new xpac, but there is necromancer as new class (paywall). Anyhow you can play with other nec even if you don't buy the pack.
Wizard is a good class to go, Nec is funny tho.
I started the season with barb and i'm enjoyin the gameplay