You get although a high amount of gold at gamble npcs for the valuable elixir.
If you use this elixir it gives you a defense, hp and mana bonus for about 3 min.
But you can use 3 flags with one rare shilds in cube and the shild will get 2,5 Damage/Level reflected to Attacker.
For further recipes read the readme
P.S.
You can gamble at normal, nightmare or hell, there is no effect from the difficulty level. You get the same gold for selling and have the same chance for good items.
It only depends on your charlvl