It’s a little confusing, But I’ll do my best to explain from my understanding.
Everytime you play, any rewards you don’t win get added to the pot. For example: if your match has a maximum of 7000 gold and you only win 6000, the remaining 1000 goes to the pot. In addition to this, the pot also grows daily by a set amount regardless if you play or not.
I do not believe that rewards lost from the pot match go to the next pot.