Earth’s moon would be the most logical staging area if we are going to head in that direction.
It's insane to even think of putting a manned settlement on Mars, when we haven't even proven that we can do it on our own moon.
I think:
1. We have a “orbital platform” already; it’s called the moon.
2. The moon can be used for many initial practice, planning and preparation phases of manned exploration of the solar system, including: (a) the engineering and operational questions of landing & constructing, or landing materials & components & constructing, “base camps” on solar system bodies beside the earth; (b) transportation issues from and to manned craft in orbit of solar system bodies besides the earth; (c) energy supplies & production off earth; (d) sustainability (shelf life) of living and non-living elements with neither space-craft-level shielding or a dense earth like atmosphere; (e) materials exploration on other bodies in the solar system besides earth.
3. Deep space exploration vehicles could be constructed in components on the moon’s surface, where, once completed, “take off” to space would be minimal (energy wise) compared to earth and it will also avoid the engineering and energy requirements of a separate man-made platform (which would have many of the same “sustainability” issues as on the lunar surface, with a lot more energy requirements than a lunar base just to maintain it’s artificial earth orbit.
I say - build a “moon base” and from it we will learn, acquire and improve a ton of the engineering that will be needed and useful on some “off world” human exploration of some place like Mars, BEFORE we are expending efforts going the distance to and from Mars.
The moon - our solar system exploration test base.
Meanwhile, a ton of further atmospheric exploration and testing of the Martian atmosphere can proceed with very simple Mars orbiting vehicles/satellites, without any humans yet on board and without the additional costs of getting humans there and back.