Spaceships should be made to stick to each other in space and use less engines fuel.
First they need to build space staions and solar energy plantation on mars orbit.
First constructions i would do a glass factory, and build with it 10meters wide, 1km long, triangular tunnel like building on the ground. With many layers of thin armored glass, with some gas between them.
Factory to manufacture steel, and factories to build other factories and repeat this till you get most things you need.
Robots for constructions, trains, storage for fuels, energy, food... Build lots of electric solar energy fields. Bigger and longer glass buildings..
I would do a tunnel building, and rail parallel that goes all around the planet. 1km wide 50 meters tall.
