Take the Yunnan-Tibet line. Then stay in Shangri-La for 3-4 days. Adapt to the climate of low plateau. Go to Lhasa. This will be much better. It S very convenient. Second, you can visit go to dali, ——, Lijiang, —— and Shangri-La. You can fly from Shenzhen to Kunming. Such a plane ticket should be cheaper.
Then go out and hide. If you want to visit the northwest. You can take the train out of the Qinghai-Tibet line.
You can also take Sichuan-Tibet. But Sichuan Tibet and Yunnan Tibet were in the same strain before Mangkang.
Pay attention to some carpool information and special fares. This will save some money.