Cast the earthbending creature by paying its mana cost.
When you cast that spell, you lose 1 life and create a 2/2 artifact creature token.
The earthbending creature enters as an artifact land creature due to Biotransference and Toph.
When that creature enters, it earthbends, causing itself to become a land creature with haste, putting at least one +1/+1 counter on itself, and creating a delayed triggered ability.
Activate Goblin Bombardment by sacrificing that creature.
When that creature dies, the delayed ability from step 4 triggers, causing it to return to the battlefield tapped as an artifact land creature.
Repeat from step 3 any number of times.
Resolve all activated abilities from Goblin Bombardment.