All year
A rain shell, comfortable walking shoes, a modest layer for shrines, any prescription you cannot replace quickly, sunscreen, and a plug adapter only if you are coming from outside India. Sockets are the Indian type. Cash in small notes. A power bank.
April to October
Light clothes, one warm layer, a hat for the sun, and shoes that survive wet grass. If Gurez or a trek is on the list, add a fleece and a torch even in August.
November to March
Winter coat, thermal layer if you feel the cold, gloves, wool socks, a hat, and waterproof boots if Gulmarg is included. Sunglasses for snow. Lip balm. The rental shop will not save a bad pair of shoes.