Desperately need help

Just downloaded today, quit 2 years ago. I searched but can’t find the “sweet spot” level for each rarity when to sell 1-stars, 2-stars, etc. This is my most critically needed information as I’m trying to fix my roster to farm effectively.

Also, what are the best characters I should be focusing on? Has anything changed besides Bonus characters now becoming shards?

Thank you, this is the exact post I was looking for but it didn’t show up in my personal post history for some reason!