Riku of Two Reflections + Dockside Extortionist + Eternal Witness + 1 more

Cast Dockside Extortionist for .

When Dockside Extortionist enters the battlefield, its own ETB triggers and Riku of Two Reflections triggers.

Stack the triggers such that Dockside Extortionist's trigger resolves first, creating 5 Treasure tokens.

Pay for the Riku of Two Reflections trigger using 2 Treasures, creating a token copy of Dockside Extortionist that creates another 5 Treasure tokens.

Cast Snap using two of your 8 Treasures, returning Dockside Extortionist to your hand and untapping two lands, leaving you with 6 Treasure tokens and two untapped lands.

Cast Eternal Witness with an untapped land and two Treasure tokens, leaving an untapped land and four Treasure tokens.

When it enters the battlefield, Eternal Witness and Riku of Two Reflections trigger.

Stack the triggers such that Eternal Witness resolves first, returning Snap to your hand.

Before the Riku trigger resolves, cast Snap using an untapped land and a Treasure, returning Dockside Extortionist to your hand and leaving you with 2 untapped lands and 3 Treasure tokens.

Pay for the Riku of Two Reflectons trigger with 2 Treasure tokens, creating a token copy of Eternal Witness that returns Snap to your hand on ETB.

You are now back where you started, but with an extra Treasure token, an Eternal Witness token, and a Dockside Extortionist token, and with 2 untapped lands instead of .

Repeat for infinite Treasure tokens and creature tokens.