Learn basic CG theory. Implement ray tracing and rasterization. Understand the math; I'll come up quite often. Learn how the GPU works. Learn a graphics API, like OpenGL.

For the level you see in Cyberpunk, you need to learn modern, physically-based techniques. This requires a bit more math, though nothing you wouldn't see in a CS degree. My favorite reference on PBR techniques is the PBR book, which is free online. Applying some of these techniques in a real-time setting is of course another challenge.

However, all this probably takes a ton of time and math and low-level programming knowledge for a newcomer.