How to make a unique custom Skybox design for Unity easily / Unity tutor...
How to Create a Skybox
ht I'd share my experience in general here:
Learn to Create Simple Cutscenes in Unity and Maya
When using PBR materials make sure you're using reflection probes so the materials react properly to their local environment. A tutorial on how to set them up.
Scrolling & Parallax ( Unity 2D ) - Game Mechanics - Unity 3D
How to get Volumetric Lighting in Unity 5 - Tutorial
Unity 5 - Direct Blend Trees
Dungeon Building in ORC: Vengeance with Unity3D