How can I improve an asian sauté / stir fry?
A few tips:


Marinate the meat first (after chopping, before stir-frying);
Mix the sauce first - don't just dump the ingredients separately into the wok;
Add corn starch or tapioca flour to the sauce to thicken it.  I wouldn't even call it a sauce without any thickening agent.  About 1 tbsp per cup of sauce should be alright.  (Note: The sauce should be about 50-60% water, don't use a whole cup of soy sauce!)
Add some other savoury or flavour-enhancing ingredients to the sauce - i.e. toasted sesame oil, rice vinegar, brown sugar/honey.  And ditch the oregano.
Briefly steam the vegetables in the wok - add just a little bit of the sauce, then cover it for a few minutes.  This will make them much more tender after frying.  (Note that this only applies to hard vegetables like carrots, celery, broccoli, etc. - add the soft vegetables afterward)
Add minced garlic with the ginger.  The two go together like white on rice.