I was wondering about marshalling if the only limiting factor is gold and I could marshall as many times as possible and have unlimited space for them

There is no limit to the number of different characters and locations you have in play. Gold is normally what you use to pay to play a card from your hand. There are sometimes special cards or scenarios that will tell you there can be other ways to play cards from your hand. This is all without getting into what you do with Duplicate unique cards.