You can very quickly use a ton in a stir fry. I like it most with shrimp or beef. To make four servings of stir fry with just protein + bok choy, I probably use 2-3 full heads.
Mince some garlic and raw ginger. In a small bowl, mix together soy sauce, rice wine vinegar, sesame oil, and a bit of oyster sauce. Divide sauce into two and add half garlic/ginger to one half - use this half to marinate your protein. Set aside the other half of the sauce and the other half of the garlic/ginger. Slice bok choy into ribbons. In a very hot wok or other pan, stir fry protein in a bit of oil until just cooked - remove from pan and set aside. Reheat pan and add a small amount of oil. Stir fry the remaining garlic/ginger for a few seconds and then add bok choy. Cook until just done, adding a small amount of water of necessary to steam the bok choy. Return protein to wok along to the remaining sauce. Stir until coated and heated through. Serve over rice.