Square paving slabs as load spreaders, short brick piers, thick
polythene (DPC) or proper A1 roofing felt on top as DPC.

Airflow under a shed prevents rot, moves the shed timbers out of the
ground "rot zone", and provides protection from splashback (rain
hitting ground splashes back up causing damp).

If you plan on using the shed as a work room in winter, insulate the
floor re cold feet (polystyrene jablite with whatever flooring on
top), and insulate the ceiling re sun bake & winter heat loss. A
dehumidifier will keep things dry, but are expensive to run if any air
changes per hour so vapour barrier everything.