Dear Hooligart, I have a good suggestion that might be interesting. =
Please consider Adding " Betting" to Colosseum fights. Even in many folklore/novels/Wuxia - heroes can bet "Gold" on Arena fights to earn some substantial benefit. NOTE: The amount of gold can be limited by level/league rank/fight difficulty - with top fight option giving more Gold - lets say *2 instead of *1.5. In this way, Players can earn more Gold in interesting/fun way rather than boring grind.
If implementing betting is a success, then it can be extended to Tower fights as well. So that players can get some more Gold in a less time consuming way that actually involves gaming. Amount of Gold that is required to level up Girl cards is too exaggerated as you go past level 15. Almost all of my girl cards have level up pending because of gold shortage. I see little logic logic to spend Gold on Dungeon girls because of this scarcity of Gold. No event gives good amount of Gold and even weekly league reward also has stifling amount of gold. Please think of a way to implement giving right amount of Gold as reward with events.
OR simply reward "Gold " instead of "applause" after the fight (and goals can be remained same -> a very simplified version)