Maybe not Mars! Logic dictates Lunar settlement first, and the Earth-Moon L1 point second.
Self-supporting colonies of human beings on Mars or, say, Ceres can’t be our first step into space — not if we’re going to be economical or sane about the task. Our first need is to industrialize space, outside of the earth’s deep gravity well. To live off-earth, we first need to create large scale 3-D printing facilities, general manufacturing, mass to provide radiation shielding, farms and at least temporary artificial gravity (through rotation) off-earth. Trying to do all that on Mars itself before getting it done in the vicinity of earth first is madness, at least, with any technology will have in the next hundred or years. Mars first means shipping everything needed for colonization up out of a very deep gravitational well — earth. Even if colonies on Mars are your aim, why not bring most of the tremendous amount of mass you’ll need up from the moon’s 1/6 gravity instead? It’s far more economical.
The moon is too rich in everything needed to live in space (except possibly hydrogen) to ignore. Yes, there’s more hydrogen elsewhere, and sure, it would be convenient to be able to drop down into a single spot on Mars that has permanent water ice and seasonal carbon-dioxide ice. (One of the supposedly killer-objections raised in the media against a recent Martian colony proposal was that there wouldn’t be any carbon dioxide available so the colonists would have to live in a pure oxygen atmosphere, reducing plant growth and making fire an intense danger to any colony. Nonsense, if you set up near the poles.) But everything other than hydrogen that you really need to live in space is available quite nearby — on the moon. And hydrogen may, turn out to be available at the poles, too. Lunar soil isn’t just arable — it’s super-arable. Glass, plentiful oxygen, aluminum, super-arable soil — it’s all freely available in moon soil, no prospecting necessary — just processing. If necessary, the hydrogen necessary to create water can be brought up from earth. Hydrogen is nothing if not light. Everything else you really need to live beyond the earth, the moon has in abundance.
As a matter of economics, the road that takes us away from the earth goes first through the moon, no matter where you go from there. However different it looks, the moon’s most ancient geological history is largely shared with earth, so its materials are very similar. The moon also has more solar energy than earth the receives (since it lacks an atmosphere) not less (as on Mars.) It’s closer. But there’s one more killer advantage to beginning with moon colonization: the lunar gravity well is smaller than earth’s or Mars’, so lunar materials can be boosted — by electromagnetic cannons or a moon-thread elevator — to the L1 point easily enough, from the moon’s poles. (Note that a cannon at a lunar pole aimed at the L1 point would lie along the surface.) Material shot up to the L1 point would come gently come to a stop at the top of that local gravitational saddle point, where it could be collected and processed. A similar cannon on earth wouldn’t work anything like as well, because we have a thick atmosphere and six times the gravity.
The only better location than the moon to set out from on the way to Mars or Ceres or elsewhere, is the earth-moon L1 point, because it’s somewhat higher gravitationally speaking: just barely within the gentler slopes of the earth’s gravity well. An excellent location at which to create a second industrial base from which longer journeys can be launched. The moon’s polar regions would be the starting point for any L1 project, as a source of materials; so it seems to me that logic leads us to the moon, first: no matter where you want to go from there.