two knights defense, is kind of a gambit
Best openings/gambits to use against king's pawn

Openings/gambits? Either or? I'll assume you want gambits. For Black to play a gambit against 1. e4 you will need several as White can steer the game. Falkbeer Gambit is fun but white must play 2. f4, etc. No single move response guarantees your gambit. Can you give us some idea of where you are going?
What are some consistent openings/gambits for black to use against white's king pawn opening?