Activate Overgrown Estate by sacrificing Guildless Commons.
When Guildless Commons dies, Toph, Hardheaded Teach triggers, returning Guildless Commons from your graveyard to the battlefield tapped.
When Guildless Commons 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 Overgrown Estate ability
Repeat.
This intricate loop turns the laws of material and magic on their head by using Toph, the First Metalbender to permanently reclassify your nontoken artifacts as lands, turning mundane objects into living earth. With Guildless Commons on the battlefield and Overgrown Estate ready to consume your resources, you can repeatedly sacrifice the Commons to gain life. Thanks to Toph, Hardheaded Teacher watching over your spellcasting and card movements, the death of the Commons triggers its return to the battlefield, which in turn causes the Commons' own entry trigger to bounce your cheap artifact back to your hand. When you recast that artifact, Toph, Hardheaded Teacher triggers once more to fuel the cycle endlessly, generating infinite life, landfall triggers, and sacrifice fodder.