The key card is present but its support is thin.
Prioritize useful support such as Wanderbrine Preacher or Silvergill Peddler.
Convoke Skyswimmer with Peddler and Preacher to filter and gain life without attacking. Duelist can untap a Merfolk at your end step.
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.
A creature tapped for convoke before blockers cannot block later. Choose whether to cast before combat or keep blockers available.
The support is missing
Favor independently useful creatures and interaction if the narrow support does not arrive.