Arrangement ideas: Move your karin statue to the center of the groups. move Karon to where the statue is now, move the archer lady to where Karon is, and Fuu's replacement to where the bow girl is. For you back row, put people with ranged attacks - I use the lizard with Keifa, the Range 3 marshmallow guys with Keifa, and the white heart guys with the Fuu. I use minotaurs in the front mid - at around level 55, they start to one shot a lot of your enemies. I use the Succubi on one side and the Fire demons on the left - they do less damage directly than some other monsters, but they aoe so if a side gets bum rushed they can clear lots of people fast. Your middle will fall, but Minotaurs will kill a lot of monsters if they get bumrushed and then they'll get peppered with arrows in the middle.
For your abilities, I use Karons crit up when units first move into my melee guys because it helps with one shotting things. Any other ability is situational.
For other rooms, try to get a decent dungeon rating - I use the fishing hole as the first room, followed by the crab boss. Left side is outhouses followed by dragon boss, and right side is another adventurer room (donation box or casino) and then land mines (the funnest trap). If you are getting hammered to fast, or if you're fighting a lot of enemies with poison, you can replace karin statue with the spa because it cleanses everyone every few phases. I do not state this as the "best" dungeon, but i was able to fully ressurect Karin on playthrough 5 this way.
Other advice: once you unlock the second row in the compass, immediately get the bonus area. The first give attacks agains this area each playthrough will get you the little gems for the compass. Makes it much quicker to start getting compass upgrades.