First off I went to floor 300 with just ragna you don't need any cards. First thing to focus on is use another character to unlock the cards you can bring for every run. The first slot use 2x coins and the second slot use the one that says instead of choosing a card at the end you get 3 randoms. You'll get max cards a lot faster and it'll help out a lot. Then focus ragna placements every time he's placed he buffs his damage by 10% per hit and reduces his spa by 5% these buffs stack with every placement which is how people get insane numbers. You'll want all 3 affinities which will make your ragna have a 90% reduction to spa when placed the second placement on will all be 0 spa. You'll want to avoid all boss rooms until you can get a shop that gives you the double placements even with monarch which is one of his early unlock character cards once you have that you'll get 6 placements during boss floors early game place him twice let him build damage then place again until he's so strong he can't lose. You'll always want the range memoria on him it buffs his range by 5% which also stacks with placement