If you take the package tour to the place like Lhasa, Gyantse, Xigaze, etc. with the altitude of 3000m, you don't need to provide the special equipment only the daily commodity required. Please find out the below list as the daily commodity which is required to be prepared for your Tibet tour:

Sun cream with the protection index of 60, sunglasses or dark glasses with a sun protection factor of 15, the lip creams and balms with SPF rating, towel, a pinch use toothpaste as a substitute, electric torch, rope, Swiss-style pocket knife map.

When planning your clothing needs for your tour to Tibet, remember, your destination sightseeing is at elevation of 3500m and your cloth must be warm enough and can be removed easy enough.

Jacket: a fiber-pile jacket is ideal for evening.

Sweater: Wool or wool mix with a high neck for extra warmth.

Headwear: wool or fiber-pile ski-style cap or balaclava for warmth. A lightweight brimmed hat is good for sun protection .Inexpensive broad brimmed straw and felt hats are sold in Tibet's city markets.
Scarf: wool or silk is best.
Mittens or gloves: wool is best.
Bandanna or handkerchief: Bring several.
Cotton underwear: four or five pairs.
Socks: at least three pairs.

Shirts: A long-sleeve shirt made of wool, flannel, or chamois, or a track-suit top. A long-sleeve cotton shirt for warmer temperatures. Bring two or three T-shirts as well. Pants: For men, one pair of loose-fitting wool pants, wool knickers, or fiber-pile pants, and one pair of light-weight cotton pants. Women should wear a mid calf dress or skirt, though pants and knee-length knickers with socks are also acceptable. Shorts are not appropriate at any time in Tibet for men or women.

Sporting shoes or comfortable walking shoes are highly recommended for all weather. Also, don't forget to bring along pile jackets, wool or wool mix sweaters with high neck, wool or silk scarf, mittens or groves, cotton underwear, long sleeve shirts and loose fitting pants. Journal, reading book, writing materials: For quiet moments.

Camera: You will regret not bring one.
Binoculars: Good for observing birds, wildlife, and distant scenery. Money pouch or belt: Safer than a wallet for keeping your passport, money, and valuable papers.
Pictures from home: Personal photographs of your children, pet, city, house, and so on are a great way to communicate with local people. Snack foods: Nuts, chocolate bars, granola bars, dried fruit, hard candies, beef jerky, and flavored drink mixes are much-appreciated trail treats.

As to the equipment for trekking, your tour operator will do the big work for you, like the tent, cooking equipment, food, car, truck and pack animals etc. Even these facilities will be arranged by the company, you still need at least 2-3 months to prepare for your personal packing. When planning your clothing needs for a trek, think in terms of layers. Layers of clothing will keep you warm, but can be removed to gradually prevent overheating. During spring and autumn the night temperature in the mountains often dip below freezing, making warm gear essential. In the summer the days can be hot, requiring light cotton clothing. Adequate wet-weather gear is also a priority during the summer. Remember that the mountainous regions of Tibet can receive snow any month of the year, and always be prepared for cold weather if you will be trekking at elevations much above4880m.Make sure that the clothing you will wear most often can be washed in cold stream water and dries quickly.