I feel like an hour cooldown on the random buff is a bit long. Also the 33% speed increase feels like a bad luck draw with how little the arena matters after a short time. Salt in the wound in a way after waiting said hour and hoping to get the 10x income buff.
Maybe some purchasable unlocks for diamonds/credits that reduce the cooldown, increase odds of the better effects, or increase arena bonuses etc?
Loving the game otherwise, fun to have open while i work and slowly advance.