The minimum specification for VRC's desktop/VR mode are a 4th gen i5/AMD FX 8350, 4GB of RAM, and a GTX 970/Radeon R9 290. However, by adjusting settings, you can run the game on a lower spec PC.
These settings have been tested on a PC with an 8th gen i3, 4GB of RAM and Intel UHD 620 Graphics.

- Force the game into DX9
Go into Steam's launch options and type in -force-d3d9. This will force the game to run in DirectX 9 instead of 11. This should help with performance as 9 is an older version of DirectX.

- Adjust Resolution
Hold Shift while pressing PLAY in Steam. The game will show a configuration window. Set the following settings:
• DesktopLow (for graphics quality)
• 1280 x 720 for widescreen or 640x400 for blurrier widescreen (use this if your PC is bad or you're having trouble playing worlds on stable framerates)
• Uncheck Windowed

(If the game is running slow in some areas on recommended spec, you can turn down the resolution too)

- Safety settings
When in game, press ESC and choose Safety from the menu. Go to Custom and turn Particles and Shaders off for ALL TIERS. If you want, you can also change model rendering in the advanced settings.

Your game should now run loads better. Be warned though, worlds with excessive detail or lots of unoptimization (like the Great Pug or Void Club) may lag your PC.

I would reccomend doing this only for desktop mode. Results may vary with VR mode.