What should I upgrade next, CPU or GPU?

Hi. I am not a very active reddit user, but I am hoping this is a good option for getting some advice. Here is my current PC:

Processor: Intel Core i5-357K CPU @ 3.40GHz

GPU: GeForce GTX 970

That is mostly what I am concerned with. I have 16 GB of RAM, and decent storage with a 1TB SSD handling most of my games.

I recently got an Oculus Quest 2, which I really enjoy, but I would love to be able to reliably play more games with it with the link cable. I don't have a huge budget, but I am not rushing to make this upgrade. I am basically just wondering which I should be looking to upgrade first. Any advice?