Activate Need for Speed by sacrificing Simic Growth Chamber.
When Simic Growth Chamber dies, Toph, Hardheaded Teach triggers, returning Simic Growth Chamber from your graveyard to the battlefield tapped.
When Simic Growth Chamber enters, it triggers, returning the artifact cast in step 1 from the battlefield to your hand, as it's a land due to Toph, the First Metalbender.
Resolve the Need for Speed ability
Repeat.
This ingenious loop transforms your cheap artifacts into a self-sustaining engine by turning them into lands with Toph, the First Metalbender. Once that type-shifting is in place, casting an artifact triggers Toph, Hardheaded Teacher to animate your Simic Growth Chamber via earthbending. You then feed that animated bounce-land to Need for Speed, sacrificing it so it dies and immediately loops right back to the battlefield via its own built-in safeguard triggered by Toph, Hardheaded Teacher. Finally, when Simic Growth Chamber re-enters, its own trigger forces you to pick up the original artifact—which is currently acting as a land—allowing you to recast it and repeat the entire sequence for infinite triggers.