The stirfry sauce i use and i use this to marinate my meats too is (note do not have accurate measurements)

Oyster sauce
a bit of sugar (1 tablespoon for marinating meat)
some salt
a bit of sesame seed oil (optional and not used for marinating)
a bit of pepper
a splash of fish sauce (totally optional)

Toss meat in some cornflour

Fry garlic then meat then veggies

Simple.