I've been learning a lot about OpenGL lately, specially with the http://learnopengl.com website and other similar websites. However, i'm still trying to understand how different shaders and techniques can come up together to create a rendering pipeline. How can i mix different shadowing and lighting techniques? How does that affect my normaç/specular/diffuse shaders? Should i create a single, big shader, with many variables... or small shaders with specific purposes? If small, how do i make them communicate with each other?

I went to the bgfx github page and went through the examples, but they are very confusing with lot's of global code laying around. Do you guys recommend any good examples of rendering pipelines being setup?

Take a look at amnesia's game engine.

https://github.com/FrictionalGames/HPL1Engine

BGFX is not the cleanest code around, and it's an absolute pain to read. Then again... it was never meant to be read I suppose. It's basically a nearly direct API meant to fit into an engine's abstraction.

Do you know something similar to BGFX, but friendlier to beginners?

As far as I know of... there's only one. But other wise nothing like that exists.

https://github.com/bazhenovc/sigrlinn

That's a nice lib. Seems like it's going to be used by all major Torque3D users. :D

Note though it's not meant for dumb firing. Meaning that if you use that library instead of BGFX, you will need to sort your draw calls.