Mr. Thompson: If you intend to use Aerofly FS 4 with VR we strongly recommend to use at least a graphic card as fast as the NVIDIA RTX 3070 Ti. Depending on the region where you fly and what aircraft or helicopter you use, these graphic cards give you enough 'headroom' for a smooth simulation. For VR it is very important to get a good and consistent framerate, and saving money at this point is something you will regret. So if you have the budget, you might even look for a NVIDIA RTX 3080 Ti.
The graphic card you choose also depends on the VR system you get. They vary a lot regarding the resolution they render per eye, so the more pixels are rendered per eye, the more the graphic card has to work. If you don't mind the more complex setup, the Valve Index is a very good system. Also good VR system with a little less setup is the HP Reverb G2. You can read about the differences here.