Clinical trials done in the West are lacking or confounded, and thus optimum doses cannot really be extrapolated from these. The best estimate at this moment in time may be falling back on traditional preparation methods, which are various:
Dried fruit extract in a 1:6 w/v ratio against liquid (95% ethanol) and administered at 20-30 drops daily
Dried fruit extract in a 1:20 w/v ratio against water, 150mL drank twice a day with meals
Eating the powdered fruit or fruit extract (this is what is usually found in pills) at 1-3g daily, with meals
Schisandra Chinensis fruits can be brewed into wines or teas as well.