If you decide to pursue perimeter drains, make sure and punch holes through the blocks and run waterlines from the block to the perforated drain. Do some reading on the subject.
I would also make sure you do everything you can to divert all water from the building before working on inside drains.
One thing is for sure, you will need to make changes if you want to use the area, and go slowly because if you make some changes, make sure they work before you spend money finishing.