Do you have a dehumidifier running down there?

The first step is keep water away from the foundation - make sure your gutters are large enough and clean. Put extensions on downspouts to dump water further out from the house. Then, make sure you don't have any areas where the dirt slopes down toward the house. If you happen to be in an area where run off occurs from houses around you, look at diverting the water with a swale or dry stream bed before it ever gets close to the house

After you have taken care of the exterior issues, then see how well you can do with a dehumidifier. Often it will take quite a while to get the basement dried up, but once it is dry, it shouldn't be difficult to keep it dry with a dehumidifier if you don't have incoming water

We had a waterproofing system put in. Expensive but worth it.