Recommended you to carry during the Mt. Rinjani trek program, all Items to be packed in a small backpack no more than 10 kg :
Quick Dry Synthetic Material :
Shirt (short or long sleeve) as the base layer, a good quality fleece jacket/woolen pullover as the middle layer, and a thick windproof jacket as the outer layer. A waterproof and windproof trekking pant is desirable and a pair of woolen gloves, beanie, and scarf for additional cold protection.
Trekking Shoes :
Mid or high-cut shoes are preferred over low-cut ones for better ankle grips and to prevent loose soils from getting into the shoes.
Trekking Poles :
Highly recommended for the summit climb as the terrain towards the summit is very steep and consists of very fine and loose volcanic soil that may cause one to slip down easily.
Water Bottle, Torch or Flashlight, Toiletries, Sun block/lotion, hat/cap, sunglasses, Spray for muscle/balm, Insect repellent, Camera, Mobile phone, and Power bank.
Packing list above assuming you are going with a guide and porters carry all camping equipment (Tent, Sleeping bag, sleeping mats, and Toilet tent), Cooking gears, food, and beverage.