How to Setup Elite Dangerous in VR
First and foremost, make sure that you know how to put on the headset properly! Dial in the correct IPD and set eye relief at the proper distance. Check and adjust fit for maximum clarity, sharpness, and comfort every time you put on the headset.
Settings depend on your PC, though, most of all on its graphics card. NVIDIA users can use GeForce Experience to see recommended settings for "Elite Dangerous: Horizons VR" in the game optimizer and create a VR profile based on that with EDProfiler (that's what I did - here's my profile for NVIDIA GeForce GTX 980 Ti).
EDProfiler also comes with two VR-optimized GUI color presets ("Dr. Kaii's Spiritual Teal" and "Grnbrg's VR Green"). These make text much more readable without ruining NPC portraits (since there's only one GUI color palette, so it needs to be optimized accordingly, i. e. "avatar friendly").
I also always activate SteamVR's Night Mode (available inside VR via Settings on bottom right of VR Dashboard, first page, top checkbox). This dims the headset until 5:00 AM or until SteamVR is restarted, so it unfortunately has to be reactivated manually each time. It reduces glare, god rays and eye strain by reducing the overall brightness. If necessary, you can compensate by raising Gamma a little in ED's graphics options.
Also set "Dashboard/Interface Brightness" to minimum in ED's graphics options or ship's functions (right panel). Makes text much more crisp and legible.
For optimum resolution, raise "HMD Quality" in the game, not the in-game setting called "Supersampling". Or just use SteamVR's own supersampling (RenderTargetMultiplier - until it can be configured within SteamVR without editing config files, use OpenVR Advanced Settings, which is an essential SteamVR tool that you should have anyways for all its other benefits), which is multiplied with HMD Quality, but affects other games as well (personally, with my NVIDIA GeForce GTX 980 Ti, I've kept HMD Quality at 1 and set RenderTargetMultiplier to 1.4).
When using ED's HMD Quality or SteamVR's RenderTargetMultiplier > 1, consider turning in-game Anti-Aliasing off. Both are a form of supersampling which is an anti-aliasing method, so additional anti-aliasing is likely redundant and only reduces performance with little to no visual gain.
Tweaks to Settings to Achieve the Best Quality and Performance
Steam: Elite Dangerous - Properties: Ensure that "Enable the Steam Overlay while in-game" and "Use Desktop Game Theatre while SteamVR is active" are OFF.
SteamVR Settings (via right-click menu of SteamVR tray icon): Performance: Allow asynchronous reprojection ON, Allow interleaved reprojection OFF! Developer: Direct Mode ENABLED, Enable Always-on Reprojection ON! Restart SteamVR for changes to take effect.
If you customized SteamVR, I suggest you reset Background, Environment, Base Station, and Controller to default. Elite Dangerous is a demanding game, you don't want such customizations (that you normally won't see anyway while playing ED) taking up precious resources in the background.
I'm a fan of the X52 (Pro or normal) since it's the same joystick the in-game model is based on. With the proper control setup and placement, your in-game hand will mirror your real one exactly, greatly enhancing immersion/presence.
I've made sure that the bindings match the in-game buttons as closely as possible so when I push a button on the real stick, my in-game representation pushes the same button on the virtual stick. I achieve amazing presence that way, it really feels like I'm inside the cockpit and piloting my spaceship myself (instead of merely remotely controlling the pilot).
I have bound pretty much all important actions on the HOTAS, thanks to Elite's built-in shift-button support (i. e. binding button combinations). That way I have no need to use a keyboard for anything except chat or galaxy search.
Later I replaced the X52 throttle with a Thrustmaster stand-alone throttle which I like much better. It has an analog stick for thrusters and more buttons/hats which are also placed better, and not such an annoying detent (I added my own velcro center detent).
Make sure to enable full throttle range in ED's control options if you want your virtual throttle to mirror the real one. Except for supercruise, where there's no reverse speed, real and virtual throttle will then match.
(Addendum: Personally, I'm not using the throttle to control speed anymore, I actually went even further and turned Elite Dangerous into a real workout by controlling the throttle with an exercise bike that works as a game controller... Yes, my spaceship is now pedal-powered! ;))
Set up like that, ED in VR is pure bliss! Especially if you fly a ship with a panoramic canopy, e. g. Keelback or Asp (get one ASAP), or something intimate like a ship-launched fighter. And remember that VR gives you "space legs" in a way, so don't just sit there, get up and walk around your cockpit or stand next to your seat while hovering in front of a white dwarf, during long-range flights within a system or when auto-docking. Those are some of the best VR experiences I ever had (and I've been into it since 2014 with Oculus DK2, now with HTC Vive, it's even better)!
Solutions to Few Annoyances
If driving the SRV makes you sick, turn on the comfort options in ED's graphics options: "Reduce Camera Shake", "Vehicle Motion Blackout" and "Vehicle Maintain Horizon Camera". Especially that last one makes a huge difference in how comfortable planetary driving feels in VR.
Galaxy/System Map: I have no problem using it in VR since it's nicely mapped to my HOTAS. However, it's vital to pivot the map a bit before using it, only then will you see where the selection cursor really is in 3D space.
Oh, and remember you can press Ctrl+V to paste into the search box. I like to plan my routes online and copy & paste the destination instead of typing it in (even bound Ctrl+V to a button on my HOTAS).
Tools that Will Improve Your VR Experience
Put any window into your cockpit as a virtual screen that can be placed anywhere within the cockpit. Some use cases are watching your favorite movies/series or clips/streams during long trips or while grinding credits, bringing up a web browser or text editor for taking notes, planning routes or checking prices, or displaying a webcam that's aimed at your keyboard. Although there's another solution for typing in VR:
Get a virtual keyboard into your cockpit that you operate with the motion controllers. Works like OpenVRDesktopDisplayPortal, i. e. you place the keyboard in a fixed position inside the cockpit, e. g. below the radar, so it's always in the same place (and auto-hides when not in use).
Control your ship like a proper sci-fi commander with your voice. I recommend using it in conjunction with one of the HCS voice packs, my favorite being Verity (the ship's actual voice since it's spoken by the same voice actress as the ship computer's).
Actually I also bought Astra which inclues a so-called "Multi-Crew" profile (not to be confused with ED 2.3's Multicrew feature) that provides compatibility with multiple voice packs at the same time, including EDDI. This uses text-to-speech to let your ship AI give you lots of useful information verbally (e. g. system state, bounties collected, etc.) and even optionally act automatically upon state changes (e. g. if your shields go down, shield boosters can be disabled temporarily, so they recharge faster).
This isn't VR-specific, of course, so I'm digressing - and it's pretty advanced so you really need to check it out for yourself to learn about the possibilities and how to use them. But it's so useful and doesn't get mentioned very often, that's why I wanted to bring it up to let you know about this.