The consumption level in Vietnam is almost the same as that in China. I can only give you a route here. How to play, how many days to play and where to play are all vague concepts to me.

Nanchang can take a train or a flight to Nanning. There are nonstop flights.

Nanning arrives in Hanoi or Halong Bay by train or bus to start your trip to Vietnam.

If you want to go to play, you'd better apply for a passport. Friends in Nanchang should go to Nanning to apply for a visa, or express it to some local tourism departments in Nanning to do it for you. One round trip a month is enough. Visa+passport+the cost of arriving in Vietnam is more than 1 points.

The four seasons in Vietnam are not very clear, but it is suggested that summer should not pass. Influenza and cholera are frequent seasons. Moreover, the weather is sultry and rainy.