In the real world, the mission has to be affordable. NASA's plan that seems to be shaping up is to place a small space station in orbit around Mars. about four astronauts live there and make a trip to the surface of Mars that last up to about 3 or 4 days than return to the station. They might be able to visit multiple locations this way. While in the station that can manage several robots that stay on the surface. This way the lander can be smaller and only needs to lander with a few days of supplies.
The station would house astronauts for a few months then they return to Earth. In a few years, a new crew is launched.
That plan is a waste of time and resources. It does not accomplish anything that warrants the expense. Such a space station would be small and cramped. The astronauts would have to spend over a year total in weightlessness with the possible exception of one short trip to the surface. Trips to the surface and back would require a great deal of fuel. The scouting of the surface can be done by large rovers designed for testing areas and moving on. It would remain.
The SpaceX Starship could have a role to play as quite a lot of bulk cargo and fuel needs to be sent ahead to the station. And landers and robots need to be sent to Mars as well.
But landing a starship on Mars means it is stuck there on Mars forever until someone finds a way to build a chemical plant that can make 100 tons of fuel that is needed to launch the Starship back to space. This chemical plant would be HUGE and would need acres of solar panels and a large tank farm. Clearly the first Starships to land on Mars will never take off again. Not until that rocket fuel factory is build and operational.
As pointed out, Robotic supply ships can land on Mars full of supplies and be used as habitats. It will be a very long time before there is anything produced on Mars worth sending back to Earth in a spacecraft. Intellectual property can be sent by radio.
So,.. the first mission to Mars will not land the Starships. They will be used to move cargo to the station. Or maybe to move the station itself to Mars.
There is no way they could send an orbital space station large enough to store significant amounts of supplies, and there is no point in doing so. Since the supplies need to be sent to the surface, send them down as they arrive.
They are never going o send 100 people to Mars in that ship. Do the math. Each person and all the food, water and clothing and other supplies plus 1% of the life support system has to fit inside 10 cubic meters. All the supplies for a two-year mission plus the stuff needed on Mars (spacesuits and other gear) all in a 2.15-meter cube.
Of course a spacecraft for colonists would be SpaceX Starship Super Heavy, or a convoy of 2-3 SpaceX Starship could be sent together. “as envisioned in the 2017 design unveiling, the Starship is to have a pressurized volume of approximately 1,000 m3 (35,000 cu ft), which could be configured for up to 40 cabins, large common areas, central storage, a galley, and a solar flare shelter for Mars missions plus 12 unpressurized aft cargo containers of 88 m3 (3,100 cu ft) total.“
Supplies for use on Mars would be sent ahead of time. Also, since it would be a one way trip, the colony transport ship(s) would only need supplies and life support for 6 months, not two years.
Do the math.
Think about you, a spacesuit a two year supply of food and water and toilet and shower and cooking space. You would not be able to move. I'd say six astronauts at most.
Again, a one way trip with supplies only for the trip to Mars, would allow a LOT more room for passengers.
Any round trip missions would waste huge amounts of money and resources. With limited funding, round trip missions do not make any sense at all. Send enough supplies ahead of time, send enough people to establish a self sufficient colony, and start a new life on Mars.