Well, honestly, for 8 platinium fragments, I would do it. 1 plat ticket = 300 kobans, 8 fragments = 270 kobans, 50 tries = 5,4 kobans per try in average. Not even counting the exp.
TBH, I discovered the gold location in beginner dungeon when you told about it. Missed it at first and didn't try again until you said something about it. I still managed to push this far because:
-The easter stage still gives a lot of money (it's better per try in average than the gold stage)
-I did the 2nd star nearly everywhere, giving lot of money
-I pushed the story as far as I could. Boss gives a lot of money the first time (around 150K/240K per map)
-I focused on the castle and the residence. My church is lvl 13, my dojo and my barracks are lvl 20, port is lvl 10, forge is lvl 15, etc.