The key card is present but its support is thin.
Prioritize useful support such as Ajani's Pridemate or Dazzling Angel.
Cast Dazzling Angel before another creature or Cat Collector. Its life-gain event grows Pridemate or Panda; later Food can provide a separate event when the mana and board make it worthwhile.
Your deck enables the plan but is losing the early turns.
Take a castable early creature or efficient answer before another expensive payoff.
Fiendish Panda gets one counter per life-gain event, not per life gained. Its death trigger uses last battlefield power and excludes Bears; simultaneous lethal damage happens before new counter triggers.
The support is missing
Favor independently useful creatures and interaction if the narrow support does not arrive.