Dungeon Farming Every 25 stages is a difficulty. The stage 16, 41, 66, 91 are the best stages to farm upgrade stone with enhanced on. They give 15 stones per run and cost the least in the difficulty.
Stage 1, 26, 51, 76, 101, 126, 176 are the best way to farm helmet for your hunter. There’s a small chance to get Ancient Helm starting from 126th floor and Primal Helm starting from 176th
So good luck.