1. Start up a space resource company aimed at space mining or buy one.
-Make the core of any mission to moon, mars or outwards about collecting resources for earth to advance the economic growth of humanity.
2. Give up on using star ship to go to mars. Maybe the moon? Anything more is a joke.
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3. Use Falcon and Starship to put things into orbit.
-As in build a couple of planetary ships that are powered by nuclear power that can hold 15-20 people, landing vehicles and sustain a long term mission. Such a ship could easily be refueled and used dozens if not hundreds of times. Lets be honest...The navy doesn't use a ship once but thousands of times...Build around that concept.
This how you get to mars. Build the infrastructure to do so! Forget the rocket for more then getting such into orbit.
The mission would be centered around resources. Believe me you're not going to build the economic case without gaining a profit! That is the cold hard truth.
Also lets be serious...If you want to build cities on mars = you have to be able to get people there within a reliable way and move around resources...Star ship isn't doing this. Only good at moving resources and people from orbit to surface or in reverse.