I made a tutorial a long time ago for that very issue
How the GS map Works
I muted myself during coughing fits to save your ears. that is also why my mouse goes nuts at times through the video, lol.
What I forgot to mention in the video is the effect on the blue wavy glass is done with a NG map. Instead of a regular NM. but generally speaking the normal map or its variant is what you use to create depth with the gs map because the RN map does not work with the GS map effect.
Here is an example of the texture set for the blue wavy glass effect.
I also would like to point out calling the _GS map "glass" is very misleading to every one. Instead we should start calling it for what it actually is, _GS = Glowing Solar effect. As it does reflect the sun and the moon on the object in question regardless on it being transparent or opaque.