The difference in temperature between the ground and the summit is 20 degrees celsius (68 degrees fahrenheit) during the official climbing season. This means you will experience both winter and summer in the same day.
Prepare for cold weather, and choose clothes that allow you to adjust your body temperature.

Hat/Cap

A hat (or cap) is necessary to protect from the strong sunshine. Choose the one with flanges. Chinstrap is also helpful against winds.

Sunglasses

Sunglasses can protect your eyes from sunshine. They can also block dust in case you wear contact lenses.

Gloves

Gloves are necessary to prevent you from getting injured.
They can also keep your hands clean and warm.

Upper Wear

Bring long-sleeve shirts and sweaters so that you can adjust your body temperature. Choose the inner clothing with hygroscopic materials.

Pants

Long pants are recommended. Choose flexible and hygroscopic materials.

Rain Gears

A waist-belt type is recommended as it doesn't put much stress on your shoulders. A rain suit (a pair of rain jacket and rain pants) is the best to protect your lower body from being wet.

Socks

Bring a couple pair of thick socks to avoid blister.

Shoes

The trails are mostly rocky and sandy, therefore a pair of mountain-climbing boots or trekking shoes with thick sole are recommended. Waterproof, high-cut boots are the best.

Walking Stick/Pole

A walking stick (or pole) helps your climbing greatly.

Others

Cash (small change) is necessary since you wouldn't be able to use a credit card at the mountain huts. Although beverage and foods are available at the mountain huts, it's better to bring some bottled water and food (snacks) as they are expensive at the mountain. If you climb at night, a flashlight is essential. Some people suggest a headlamp is even better since you can use both hands freely. In a day time, the sunshine is very strong and there is almost no shade on the trail. Therefore it's nice to have a sunscreen in order to prevent sunburn. Medicine, bandage, and toilet paper are useful just in case.