Here is the full list of all 20 Gamble Tower achievements.
Defeat the Orbots.
Defeat Noxaerudeux.
Defeat Eskyuven.
Accumulate 5000 Gold.
Accumulate 10.000 Gold.
Accumulate 50.000 Gold.
Accumulate 100.000 Gold.
Spend 1000 Chips on Stebax.
End the expedition in Success once
End the expedition in Success 5 times.
End the expedition in Success 20 times.
End the expedition in Success 50 times.
Reach max level with every clan.
Unlock every single unlockable on the Unlockable List.
Find the Gambler on the "top" of the tower.
Find the Janitor.
Burn Magic Spark while having 0 mana.
Survive an encounter with less than 10 HP.
Burn an Aseptic orb.
Finish a combat while losing 3 Gambles.