I haven't been lucky with my basements. I had them built correctly with both interior and exterio drain tile and Thoroseal on the walls. It costs less than 10% of what a retrofit "waterproofing" system will cost.
I was lucky - my last 800 inspections/investigations had no basements (Katrina), but I do have a new respect for mold and and what people can create without knowing what they are doing.
Obviously, a duhumidifier will help to eliminated some of the effects of the moisture. If you have excess humidity, It is wise to have some professional consultation to determine the cause. Usually it is far cheaper in the long run when you consider the problems caused for the home and contents. A typical dehumidifier can only circulate so much air and solve only a few problems.
Some procative measures like sealing joints with hydraulic cement and a proper wall coating (not just a masonry paint) go a long way to eliminate moisture.
Proper air flow with adequate supply and and excess air returns do wonders. If you have a good furnace, run the fan constantly whenever in the heating or cooling mode. It provides a great degree of confort and usuabilit for a finished basement room.