Exactly and soil is just one tiny link in a whole ecosystem. The primary problem is how to create a planet enveloping magnetic field to help protect your gains.
Discounting that I think I would start by putting an inflatable dome over a crater in a low lying area just to see what kind of temperature can be attained by normal solar heating and if any moisture migrates out of the soil. You would have to heat the dome at night and condition the soil but that’s the way I would start.
I did find an article about growing things in lunar and martian soil analogs. http://www.spacesafetymagazine.com/spaceflight/space-food/wageningen-ur-study-possibility-plant-growth-mars/
To me its all interesting to ponder but I have unlimited imaginary funds.
One problem about the ol’ Red Planet: terrible ass wind storms. Wind speeds of up to 400 mph are common and they can last weeks at a time. All that silica, iron, rock and Lord knows what else flying around... forget it. Thanks for the link. I have an imaginary space ship but dang it, I need a new ion- drive engine and wouldn’t you know they cost a bundle. Could you spare a few million? :-)