Activate Goblin Bombardment by sacrificing Reassembling Skeleton.
When Reassembling Skeleton dies, Pitiless Plunderer and Fumulus trigger, creating a creature token and a Treasure token.
Resolve the Goblin Bombardment ability.
Activate Goblin Bombardment by sacrificing the creature token.
When the creature token dies, Pitiless Plunderer triggers, creating a Treasure token.
Resolve the Goblin Bombardment ability.
Activate the Treasures by tapping and sacrificing them, adding 1.
Activate Reassembling Skeleton by paying 1, returning it from your graveyard to the battlefield.
Repeat.
This clever loop uses Goblin Bombardment as the primary outlet to continually hurl your own creatures at any target. Pitiless Plunderer and Fumulus, the Infestation act as the engine's catalysts: every time your nontoken skeleton hits the graveyard, Pitiless Plunderer generates the mana-producing Treasure you need while Fumulus rewards you with a sacrificial insect token. By recycling Reassembling Skeleton from the graveyard with that generated mana, you sustain an endless cycle of sacrifices, damage, and life manipulation.