Wear good woollens, sports/trekking shoes, sunglasses, sun protection cream, lip balm, a cap for protection from sun, warm socks. Additionally, you may bring a muffler, gloves, a warm cap, windcheater.
Please note that weather in Ladakh is unpredictable. The temperature here can drop suddenly anytime. You can be comfortable with sunshine in the daytime but temperature can be too cold in night time, especially at Pangong and Tso Moriri.
Even the day temperature at Pangong, Tso Moriri, Chang-la, Khardung-la, Sarchu, Taglang-la and other mountain passes will be too low.