Can you tell me the best characters to farm?

Fair enough. I have put a couple bucks in, too. I really enjoy the game so they've earned a little $ from me. I probably spread myself to thin farming other characters (Mahl, Nighsisters). I have farmed Phoenix heavy from the beginning but didnt' quite have enough of them leveled up high enough for 7* R2. I've heard some say they had a 7* team after about a month, which means I was clearly not putting all my resources to it. I'm still not a STH fan, but that's just a personal opinion.