You meet the Trader upon entering the Daily Adventure. You can exchange goods from him for a special currency: Opals.

Opals can be found in the chests on a Daily Island. Use hints in the resource menu to locate them.

The number of goods available for purchasing from the Trader is limited. However, the goods are restocked after starting a new Daily Adventure.

The Opals collected on previous daily islands can be spent at any time in the future.