What to Buy:

Your best option is to pick up the Ultimate Edition on sale with all of the DLC, but you can get by with the base game and pirated DLC.
Don't pay full price for Assetto, it goes on sale pretty often.

General setup:

Make sure to set your rendering mode to OpenVR or Oculus in the video settings and disable Crepuscular rays (Sunrays if you're using Content Manager).
Race department has a list of recommended tweaks you can look at as well, but a lot of these come down to personal taste.
https://www.racedepartment.com/downloads/assetto-corsa-vr-guide.19037/
Content manager is a much better launcher than the default one, and the free version has all of the features most people will need.
https://assettocorsa.club/content-manager.html

Extra visual tweaks:

You can install the custom shader patch through Content Manager under Settings>Custom Shader Patch, which improves lighting and adds a bunch of small fixes.
The Sol mod allows for improved weather, which lets you race at night and more.
https://www.racedepartment.com/downloads/sol.24914/

/vrg/ multiplayer server details:

NA Server:
Server: vrg racing
Pass: tfwnodriftfu
Mods: https://mega.nz/#F!IgMnDK7Y!16gzEjZRZsea9QE3NDQg6Q
We race on Wednesdays at 8PM Eastern Time, but the server is almost always up if you want to use it for anything.
Drinking and driving sometimes happens on Fridays

EU Server: (only up when races are going on)
Server: VRG EU Racing Club
Pass: 6969
Mods: https://mega.nz/folder/7mYl0Q4S#_Hz0mVfCrvk2CMcrRn83hQ
EU races are done at 18:00 UTC every other Monday

Both NA and EU servers use the voice.vrg.party Mumble server for voice chat since Assetto doesn't have built in voice chat support

Time Trial Server:
Server: vrg time trial
Pass: tfwnodriftfu
Mods: https://mega.nz/folder/51UwSJ5L#yojjZdETcm95G2DMdKzSBQ
Current Leaderboard: http://198.23.223.127:50041/lapstat
This is up almost all the time for some friendly competition.

All of the DLC should be available here if you're missing any of it:
https://mega.nz/folder/BBwxhS6D#4jJIfs6omnJUaJfsnqPqGQ

If you want a physical wheel:

T150/TMX is usually the cheapest decent option.
G29/G920/T300 are generally the recommended entry level options.
If you're fine with a used wheel, you can try looking for a DFGT or a G27.
The /ovg/ hardware guide has a lot more information if you want to go more in-depth:
https://docs.google.com/spreadsheets/d/1uLKMbKwweUZ3QvFeNs8UeycZbDyo0McxGj7T6uTaTNo/edit#gid=0

If you want to use your VR controllers as a wheel: