Growing grass in Florida?

I live in SW Florida, around the foundation of the house that does not get much sun was real sandy. So I put down a good amount of top soil, let it settle for some time, and I bout grass seed that was recommened to me at the local hardware store for our area which was a scotts southern seed. It's been about 4 months of watering, and grass has grown, but by no means does it look full and you can see big gaps between the grass. Should I just keep putting seed down until it fills in better?