Me, I've concluded that it's almost always good to start off building some metro lines, regardless of what the scenario objectives are. Even with only a few ten thousand at start you should be able to afford 3 or so stations, and more if you're ballsy enough to pull the loan-lever. Mind you, metro lines don't need to loop around at the end like tram lines, so you can keep gradually adding new stops to the end of a line without having to demolish anything you previously built.
First, metros take care of long-distance travel. A passenger doesn't pay per distance, a passenger simply pays the fixed fee once upon boarding. Meaning that a passenger traveling a long distance is a liability who uses up space that could be used to transport several passengers. If there are metros available for long-distance travel, people will prefer them over buses or trams for that, simply due to being faster. Leaving your buses and trams with the more profitable shorter-distance passengers.
With a network of metros for longer distances, you can let buses operate within smaller, closed areas centered on a metro station. Then you have a nice symbiosis going on: The metro diverts away stupid longer-distance travelers from your buses, and your buses bring passengers to your metro stations. Also, the metro reduces the amount of traffic on the streets, allowing your buses to travel faster and serve more people.