The key card is present but its support is thin.
Prioritize useful support such as Agent of Atlas or Crimson Operative.
Attack with a prowess creature while leaving Take Up the Shield available. The spell produces both prowess and a permanent counter if the creature survives.
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.
Too many tricks leave nothing to target. A spell that creates no body is not an early creature even if it costs one mana.
The support is missing
Favor independently useful creatures and interaction if the narrow support does not arrive.