Above ground garden? Help?

[jemshkoj]

I have an above ground garden in my rented yard, not getting too far with it, it has an abundance of seaside daisies in it, that turn black in winter, (now), I just cut them back, the soil is very sandy, recently bought a couple of bags of sheep manure, is this going to help. The garden is about 10 ft x 10 ft round, with a pretty ordinary stone wall, starting to fall apart, thanks for your help