If you have a damp basement a dehumidifier will not be up to the task. If the dampness is caused by something you brought in, like a year's supply of firewood then yes, it can help.
I would expect that the moisture is actually coming up from below and the only "right" answer is to dig down, put in drainage tile and then the slab would need to be sealed for moisture as well. Not a small job. What can also be done and was a job that my son had for a few years is to put in a perimeter drain out the outside of the foundation and then waterproof the foundation from the outside. Less chaos to the interior and no matter which route, time consuming and expensive.
A key issue with moisture in a space is ventilation. If you are committed to having this be a livable / usable space then that's problematic. Crawl spaces were common on most builds though. If you were to insulate the underside of the main floor and then open up the space to cross-breezes then your mold problem would probably get reduced at least but then it wouldn't be usable for anything other than storage of items that can take the cold and a bit of damp.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells
