The "get a good pair of shoes and a good bed for when you are not in one you are in the other" advice these days extends to good mouse, good screen and good keyboard.
Gamer chairs are generally trash compared to proper office chairs. Better than a dining room chair for most of what I want but rarely worth the price tag.
While I said good mouse most gamer stuff is junk or equalled by far cheaper devices.
Good keyboard. I have an ancient Acer mechanical thing and it is wonderful. Don't need my keys to light up as I a) know how to position my hands (not to mention the little bumps on f and j) and b) even if not the light from my screen is more than enough.
Never found the need for anything else. I have a controller for those games that can take to it but that is usually just whatever is good at the time (once was a PS pad adapter, today is still a 360 pad though some do go in for the PS4 one) but can happily do without one for most things that are not fighting games.
I can see some liking driving setups or mech setups but generally eh until you get to silly money.
If some Silent Scope machine fell off the back of a truck tomorrow I would not say no but it has to get to that level before I really care about lightguns.
Maybe in the future VR googles, an in place treadmill and whatever else will be in but that is in the future (minimum of 7 years from where I sit, more like 12 before any real chance of major traction).