You control at least four lands, three of which are mana-producing.
Steps
Activate
Squandered Resources by sacrificing a mana-producing land, adding one mana of any type that land can produce.
Repeat step 1 at least two more times, and more times if desired, ensuring to leave at least one land on the battlefield.
Activate
Emiel the Blessed by paying ({3} magic symbol) , blinking
Lumra.
When
Lumra enters the battlefield, it triggers, causing you to mill four cards and then return all land cards from your graveyard to the battlefield tapped.
Repeat.
Results
Infinite blinking.
Infinite ETB.
Infinite landfall triggers.
Infinite LTB.
Infinite mana lands you control can produce.
Infinite self-mill.
Put all land cards from your library and graveyard onto the battlefield tapped.