Read the Physically Based Rendering book for an understanding of the fundamentals.
Then write your own renderer, implementing basic versions of each effect, on a modern graphics API. Once you get the basics working (lighting, shadows, AO, bloom, deferred shading, PBR, foliage, terrain, etc), then build an understanding of where the GPU cost is going and try to optimize. You’ll learn a lot along the way.
2 Likes