Exquisite Difficulty

The difficulty changes a lot depending on the equipment combination. Personally, I find it stable with 1 melee weapon (sword) and 4 ranged weapons (bow/staff). Let me know if you have other combinations. You can use the melee weapon as a decoy... but it's not always the case, so strengthening the melee weapon while also increasing the attack power of the ranged group with moderate evasion (or HP) might make it stable. If you tend to fall easily, go for Main Attack x Sub Evasion type equipment. If you need firepower, I personally found Main Attack x Sub Critical type equipment to be good. Equipment rarity should definitely be increased. Check the shop regularly, and if there's gold equipment, buy it even if you have to use diamonds. Anyway, you'll run out of gold, so watching ads that increase gold will make it easier to progress.