Dummies guide to fast levelling a new (seasonal) character in Diablo 3

Backstory: So, here I am, all amped to start season 18 of Diablo. I log in. I click “new seasonal” character… or not, because we have to wait until 5pm. "Why you do dis to me, Blizz!?" What to do? I was deciding between practising languages on Duolingo, or playing...