The weight rule is the whole secret. Everything is available in towns along the way, and pilgrims who start with 25 lb packs mail half of it home from Pamplona. Choose quick-drying fabrics so one set washes in the sink each evening while you wear the other; cotton stays wet and causes blisters. Footwear is the one place not to economize: trail runners or light hiking shoes with tread, worn for at least 50 mi before you leave, bought larger because feet swell by late morning. Sandals rest your feet after the stage.
For women the list adds two or three sports bras, a light skirt or dress for evenings and Mass if wanted, and menstrual supplies, easy to buy in Spanish pharmacies; a pack fitted to a woman's torso length and hip belt matters more than any single item. For men the only extra is a razor, and a second pair of hiking pants rather than shorts in cooler months. Everyone needs a small toiletry kit, sunscreen, lip balm, earplugs for albergues, a headlamp, a phone charger with a European adapter, clothespins and cord, and a copy of the passport.
By season: in April, May, and October add a fleece or light puffy, gloves, and a warm hat, and in the Pyrenees or Galician hills rain pants and waterproof shoes; from November through March carry a real sleeping bag, since many albergues are unheated, and expect the Napoleon route over the Pyrenees to be closed from November 1 to March 31. In July and August cut to the minimum, carry two liters of water, and start at first light. The existing page on training for the Camino explains how to test the pack.