The must of China should be Beijing, Shanghai, Xian, where you could see about Chinese history as much as possible, including the Great Wall, Terra-cotta Warriors and Horse and the modern China. If you would like to see more natural sceneries, please go to Suzhou and Hangzhou around Shanghai or Guilin and Yangshuo. You'd better have a look of this website's recommendation on the Best China Tours(https://www.travelchinaguide.com/tour/best-china-tours.htm) .