This sourceforge project contains many samples from the course, Goldsmiths Computer Games And Entertainment MSc.
Lecture notes and many other pointers are available at
https://www.doc.gold.ac.uk/~mas01at/lecture_notes/
To get started, have a look at the triangle sample
This shows you how to draw a triangle in OpenGL ES2, the graphics API used on most mobile devices and by far the most common way to draw 3D graphics.
The samples build up to more complex examples such as shadow maps, bloom filters, resource management and porting to the Google Native Client.
Writing games is a very different process from writing demos. It is far less important to know about the latest GPU techniques than to know how to manage an asset pipeline or deal with unreliable network connections
Delivery of games is all about networks in the current era of smartphones and web apps.
We reccomend using Unity as a prototyping tool as it covers all the basics and some of the corner cases. But to create really great games requires knowedge of how systems like Unity, Gamebryo or Unreal work.