All the hardware is already included so you can start using it. You'll just need to register your "Facebook" account to be able to use it and if you want more comfort you can buy accessories like the Elite with battery or even the Bobovr S3 PRO Battery Relief Strap which has a removable battery that you can buy separately. If you want comfort then the Elite is top and if you want comfort and autonomy then the Bobovr S3 PRO Battery Relief Strap is top.

As the two previous speakers have already mentioned, all the hardware is basically included. The only thing you need is a Meta account, but this is free and can be created online. I also got the straps for the controllers --> Meta Quest 3 / 3S Activity Straps
The Elite Strap is much more comfortable and easier to adjust, and since I wanted even more battery life, I got the one with an additional battery --> Meta Quest 3 / 3S Elite Strap with Battery
If you want to share the HS with other people more often, or just don't want to worry about cleaning the face pad --> Meta Quest 3 Headset Inlay Sillikon
And because I like to keep everything tidy and in one place, I also got the case --> Meta Quest 3 / 3S Carrying Case

Nothing more. It works perfectly on this scale. However, I still recommend the Elitestrap with battery, as it is much more comfortable and balanced on the head.