means "You can bet money on that", showing that you are 100 percent agree with what another one has just said, and you think what he/she had said is true.
a player: We will beat xxx(another team) next time!
coach: you bet!
Said when one is 100% for the cause, even if the cause is unknown. Also said to make the leader feel they have a persons 100% trust, even if not entirely true.
Jon: So everyone is good for it
Cody: (Waking Up)
Jon: You good for it Cody?
Cody: You Bet