Where I am learning from.

I am starting to grasp how much I don't know about my interests and that I have a long way to go. For this reason I will not write extensive tutorials on this page.
But what I can do for people who stumble onto this page is share some external links that helped me develop my skills.

Shaders

The book of shaders

In my opinion, this is the first place to start if you want to learn how to write shaders.
The book of shaders by Patricio Gonzales Vivo and Jen Lowe.
While it will not teach you how to write shaders in Unity or Unreal it will give you the mathematical foundation that is needed to do them anywhere. The site is interactive and simply a great start for apsolute beginners.

My take on shaders

If you are searching for a quick and easy way to learn the basics of writing shaders inside Unity engine then this site is for you:
My take on shaders by Harry Alisavakis
It's a blog which covers a lot of solutions for most stuff why people want to learn shaders for. It also covers stuff like world space coord's, view direction, normal vectors, depth textures ect... which aren't touched on in The book of shaders.

Lighting models from Lambert to PBR

While this blog is also for Unity you can learn about lighting models from two posts: Shader Lighting Models and Physically Based Rendering Algorithms.
Blog by Jordan Stevens
The knowledge from those two posts can be easily applied anywhere.

PBR and envirmental effects

A great read about PBR and enviormental effects.
Blog by Sebastien Lagarde

Art of code youtube channel

For procedural generation of images using reymarching allgorithams this is the place to start with:
Art of code
Thank's a lot Art of code. The start of anything new is always hard and you made it easy.

The father of shader art

This list wouldn't be complete without mentioning the person who started it all and who is inspiring people around the world to push the limits of what is possible with code. I am of corse talking about Inigo Quilez:
The father of shader art

Writing your own game engine

Game engine by thebennybox

A great 60 part youtube tutorial about writing your own game engine from start to finish (if it's ever possible to finnish a game engine):
Game engine by thebennybox
A shame that more people dont have the tenacity to go through it all. Thank you a lot thebennybox.

Learn opengl.

If it weren't for thebennybox. This would be the place to start. Of course it's still worth the read:
Learn opengl

Computer graphics from scratch by Gabriel Gambetta

A great read while riding the bus as it's using pseudocode:
Computer graphics from scratch