I'm new to the game and the core rule book does not specify if I can just play them without using any gold or if I use one per turn

Man of the Nights Watch said:

Each event card will tell you when you can play it, what costs have to be paid, and if there are any limits on playing another. If any of those things aren't specified (timing always will be, limits are fairly rare, costs are kinda 50/50), you don't have to worry about them.