Trip to China where to fly into?

Im working on the backbone of the trip. Cities, towns, day trips etc. I have been looking at somewhere of the itineraries that folks have posted and their originating city where they started.

Can someone suggest where to start if I was coming from the east coast of the US. This is a 30 day trip starting somewhere in China and then leaving from Thailand/Vietnam which is the 2nd half of the trip. Of course I could also make it the 2nd half of the trip if need be. Essentially im think west to east and back home or it doesnt really matter. Just trying to see some thoughts that may include pricing, connection flights. Pros and cons that I may be missing.