A few months ago I posted two articles on gamasutra about some techniques and tricks used in Angest for GearVR. Using those helped us to achieve the good graphics and performance seen in the final release of the game. You can check them here:
In this first article, I talk about occlusion culling and tricks used to reduce draw calls.
In the second article, I talk about overdraw, texture compression, fake dynamic lighting, color grading and some tricks with cubemaps.
I might revisit some of these topics with more details in the future.