The key card is present but its support is thin.
Prioritize useful support such as Pothole Mole or Dredger's Insight.
Use Pothole Mole or Dredger's Insight to fill the graveyard and preserve land drops. Cast Chitin Gravestalker at its reduced cost, or return a milled threat with Carrion Cruiser or Broodheart Engine.
Your deck enables the plan but is losing the early turns.
Take a castable early creature or efficient answer before another expensive payoff.
An artifact creature card reduces Gravestalker's cost once, not twice. Do not exile every graveyard card for another benefit when your discounts and recursion depend on keeping them.
The support is missing
Favor independently useful creatures and interaction if the narrow support does not arrive.