I can recommend Terra Invicta as a very realistic grand strategy game demonstrating it nicely - you will never lift the thousands of tons needed for just a single ship in your fleet to protect the Mother Earth from aggressive extraterrestrial invasion.

But plop a few mining complexes (each couple dozen tons IIRC) on the Moon or near Earth asteroid and the tables turn quite quickly. As now you can build more station from extraterrestrial resources, which mine said resources and it goes from there. :-)