We strongly advise you to take your luggage in a backpack (with inner frame) and the total weight to be no more than ten kilos per person. A compact 'weekend bag' of the same weight is also possible. Think about the steep stairs of Chinese stations, the limited luggage space in trains and buses, the many unpaved streets and the lack of an elevator in the simpler hotels.
As for your clothes, we recommend you to take practical clothes that can easily be combined (layer upon layer). We ask you (in your choice of clothing) to show respect for the local culture. Thus shorts or skirts and tops in Buddhist temples are not appreciated. In most hotels a laundry service is available.
When composing your luggage, consider for example: a towel (for the more simple guesthouses and family stays outside the big cities), walking shoes, flashlight, water bottle, sewing kit, washing kit, universally valid adapter, travel guide, adequate photography equipment, sleeping bag liner, toiletries, shower slippers, swimwear, alarm clock, writing instruments, scissors, cup and knife, sleeping bag (in Tibet, the lack of sun throughout the year makes it very cold, especially at night when the temperature can drop below freezing point).