You didnt mention if you shed kit comes with a floor or not some do not.
If it does just level 4 solid cinder blocks at each corner and one in the midde
of all sides. There is no need for footings for a shed. If you bought a prefab
from Home Depot they set it on bricks that't It. If your kit has no floor you
can fraicate one out of pressure treated lumber. I would use a minimum of 2X6's
16 in on center and place this platform on solid cinder blocks. Lets not go
crazy here. It will last longer then you will!