With the game open, toggle to desktop and launch the SDK (you should have it downloaded already - I created a desktop shortcut for mine as I'm getting started on modding). Then launch FireTuner.
Go to the "Active Player" tab and toggle back to the game. Give it a second to connect and when you toggle back to FireTuner, the fields should be populated (gold, culture, etc).
Change the gold value, go back to the game, you should have what you wanted.