The gravity of Mars is not sufficient to sustain terraforming for any important length of time. Instead, we should Martiaform the planet. That is, dig down below the surface and inhabit the subsurface of Mars. ... Unless of course someone else has already accomplished that to a great degree.
How to maintain a thick atmosphere with low gravity and no magnetic field. That’s the problem. Certainly sub-surface is an alternative to making the surface livable. And I think that’s certainly the way to go on the moon.
But maybe when we’re really ready to colonize Mars (as opposed to the silliness of going there now) we’ll have some tech we can use to mitigate the surface problems.