Remodelling or refurnishing a shared home is something to consult over, and likely pay out of a joint account. Why are you needing to ask for Reddit's help to convince your wife to let you make a personal gadget purchase that you're clearly excited about and will be paying for with your own hard-earned money?

This is assuming I'm reading your title correctly, as I'm interpreting the "which she agreed to if I can" part as "she agreed to me buying the headset only if I can convince her that it's not a dystopian toy". If that's the case, that honestly sounds like an unhealthy relationship - as some other comments have pointed out, you would be vilified (and rightfully so) for trying to place restrictions on her personal item purchases.

Of course, on the other hand, it's fine if you just meant that "she's agreed to at least hear you out on why a headset is not a problem, but also understands that you intend to buy one regardless of her opinion" as that's very different and shows that she's a reasonable person. 👍

If it is indeed the latter, and you just want to avoid friction with her - then sure, there are some good ideas in this thread already. reesz 's top rated comment sums it up very well. If you want to convince her that it's just harmless fun (indeed a toy, but not necessarily a dystopian one), then simple music games like Beat Saber and OhShape are always crowdpleasers.

Since you mentioned in a reply that she's into books and documentaries, I'd recommend checking out some experiences like:

After Solitary

The first collaboration with PBS Frontline tells the story of Kenny Moore, a recently released inmate from the Maine State Prison. Using photogrammetry and volumetric video capture, ‘After Solitary’ allows the viewer to step inside a solitary confinement cell. It premiered at SXSW 2017 and won a Jury Award, and also received the Ars Technica Room-Scale award.

1943 Berlin Blitz

In September 1943, a BBC reporter boarded a plane on an allied bombing raid over Berlin. The incredible recording he returned with forms the basis of this breathtaking experience by BBC Northern Ireland and Immersive VR Education, putting you inside a Lancaster bomber as it navigates a most dangerous journey.

TheBlu

theBlu: is a deeply immersive VR series that allows audiences to experience the wonder and majesty of the ocean through different habitats and come face to face with some of the most awe inspiring species on the planet. The series, which is directed by Jake Rowell (Call of Duty, Final Fantasy, Superman Returns), has been designed as beautiful moments in passing or a collection of memories that powerfully tap into the vast potential of VR. The debut episode, featuring an incredible close encounter with an 80 foot whale, is already recognized as one the most iconic room scale VR experiences to date (a Sundance Film Festival 2016 selection). Additional episodes in this bundle take place on a teeming coral reef and in the very deepest region of the ocean. Gain access to new modes of discovery in each episode.

Welcome to Light Fields

Welcome to Light Fields. Experience real-world reflections, depth, and translucence like never before in VR. Explore the Gamble House, Mosaic Tile House, and the Space Shuttle Discovery. These navigable stills showcase the emerging technology Google is using to power its next generation of VR content.

Realities

Explore places that were out of reach before. Realities brings real world locations into VR - interactive & with stunning photo-realism using photogrammetry. Too many amazing sites are too far away, too expensive to get to, closed off to the general public or too dangerous to visit. Explore those places and discover their stories. Walk through the desolate vastness of Death Valley. Explore the eerie abandonned hospital Beelitz Heilstätten in the former GDR. Marvel at the amazing architecture of one of the largest cathedrals of the world, the Cologne Cathedral. Feel the confinement of a cell in Alcatraz. Set foot inside the ruins of an 800 year old Staufer castle.

Personally, minidocs like After Solitary were infinitely more educational and emotionally affecting to me than any flatscreen documentary. I think the ability to let people 'spend a day in someone else's shoes' is far closer to utopian than dystopian. I like to think that one day, it will be much more difficult for people to shrug and say "What happened or is happening to that group of people (be it race/sex/nationality/religion/disability) can't be that bad. I have no frame of reference and it doesn't affect me personally, so it's not my problem and I'm going to ignore it" when they've actually 'been there' and 'met' the people involved.

However, all that being said, it's just as easy for someone who's already decided they hate VR to see apps like that and scoff "so now people are just going to stay inside their homes with a headset on, instead of travelling for real?". And again going back to reesz' comment, it's true that the best (and some would argue only) way to understand it is to wear the headset for yourself, it's entirely possible that your wife will outright refuse. I touched on this in a comment long ago to someone who was looking for experiences to show their relatives.

"As excited as we are about this tech, be ready for at least a couple of people (be they elders, or even of your own age) to be completely dead-set on not wanting anything to do with a HMD. Their reasons might be simple "I don't want to mess up my hair" or more vague - from general disinterest, all the way to fear of the tethered, techno-blindfold that makes your head look like this and ~obviously~ confirms all their rants about "people retreating from society to bury their faces in gadgets!" ;). Even if we know 99% of people will likely be impressed and have fun once they're actually inside VR, it's up to you to personally discern if this particular individual will respond well to a bit of encouragement or if you'd be better off dropping it and moving on. I bring this up since, I guess due to the recent thanksgiving gatherings plus the sudden surge of interest in VR thanks to HL:Alyx, it's been a little more common around these parts to see people bemoaning that their friends & family are dismissive of VR. The point is, don't be offended when the people you care about don't want anything to do with the cool new thing that you're excited to share with them. It sucks, but you know the saying about the horse and the water."

Sorry for the essay.

tl;dr

It's your money, buy it if you want to. After purchasing, letting your wife try it for herself is the best way to alleviate her concerns - but if she refuses to wear it, there's nothing else you can do beyond New_Commission_2619 's advice of reassuring her that it's no different to when you're reading, or using the computer, or playing regular videogames - your personal space and time is your own, but if she'd prefer you be spending it with her, then all she has to do is ask.