The key card is present but its support is thin.
Prioritize useful support such as Inner Demons Gangsters or Pumpkin Bombardment.
Discard Spider-Islanders to Bombardment, remove a blocker, then cast Islanders through mayhem. Both spells can fit a turn that their normal costs would not.
Your deck already enables the plan but is losing the early turns.
Take a castable early creature or efficient answer before a second expensive payoff.
The discarded card must be cast that turn. Do not spend all available mana on the discard outlet and strand the payoff in the graveyard.
The support is missing
Favor independently useful creatures and interaction if the narrow support does not arrive.