You need less than you think — but the right less. Vehicles carry your main bag; keep a small daypack for the day's layers, water and camera.
Clothing
Sun hat with a brim, sunglasses, 3–4 t-shirts, one warm fleece, one windproof/waterproof shell, comfortable trousers, warm sleepwear for cool nights, and sturdy broken-in shoes. In June–August add sandals for camp; in May, September or October add a warm hat, gloves and a down layer.
Sun & dust
The Gobi sun is strong and the air is dry. High-SPF sunscreen, lip balm and a scarf or buff for dusty stretches make more difference than any gadget.
Power & light
Vehicles have USB charging and most camps have electricity in the evening, but a power bank keeps you independent. A headlamp is essential for night walks to the toilet — and for finding things in a dark ger.
Health kit
Personal medication, basic painkillers, rehydration salts, hand sanitiser and wet wipes. We carry a full first-aid kit and safe drinking water in every vehicle.
Nice to have
Binoculars for wildlife, a small gift from your country for host families (sweets for kids, photos of home), and a paper notebook — you will want to write things down.