I got to floor 53 in Wish Cave last night with Meowth, before I had to pull out or risk being defeated (I know now I could have used the Mobile scarf I had on me, but bleh, no reviver seeds makes me uncomfortable.)
One thing i've learned is make sure your choice has high hp. I had electrodes taking me out from a distance with sonic boom doing 55hp of damage to my...ironically, 55hp. At one point I had a herd of Tauros i'd recruited and let them absorb damage/get me exp and said farewell before they died to save reviver seeds, but it was ill fated.
It seems the joy seed idea is a good one, i'd better start stocking up. I'll try Mew next time, it couldn't hurt.