Once I came across this website I realize my brother would make a better martian than me. He has the skills to build everything on this list (alt. list) and then some. Low tech is the answer, until enough people arrive to produce high tech.
One of the arguments against mars colonies is it would take too many people to support life. However, my brother is the counter argument. Add a few other people with complementary skills and you don't need many at all. The reason for more is many hands make light work, not because it can't be done.
Update: Assume everybody specializes in making one thing. How many people do you need? About four dozen. Which happens to be the total I recommend by the second mars missions. Happy coincidence!
I should have mentioned the interlinked product ecology is important.
Aluminum without bauxite.
Steel from dirt. Easier on mars because of iron in soil and carbon in air.
Microwave steel might be better still?
The vision on mars is for underground shirtsleeve workplace Replabs.
We're not leaving out electronics. Some software to go with that.