Active job

Flat

We have a large room about 20 square metres that may have been a garage and at some stage was carpeted and turned into a living room. We have removed the carpet and it is evident that concrete floor is damp as carpet is mouldy. The concrete has join cracks across it and is slightly under the outside ground level. Is there a concrete or timber solution to stop the rising damp and make it liveable? We are after the most cost effective solution.