Hi AttempD,
It has been said about 3d modeling you can save a bad model by having a good texture but a bad texture can’t save a good model. 
The first thing I would suggest if you are wanting to understand the power of materials better is to watch our video series on Materials on YouTube.
There are several steps to creating our textures depending on what we’re trying to achieve with the models or material in question.
The basics would be as follows:
- If we’re using a mesh that needs specific UVs to lay those out and organize them,
- Create our base textures for diffuse using Photoshop or equivalent image editing software
- importing and creating a material that will utilize this texture in UE4
- using UE4 to augment and achieve the look and feel we need.
This is the basics. There are some more steps inbetween that you could do to better display your texture or other maps but again this is the basics.
There is also Normal mapping that Shoiko mentioned. This is great for creating depth to an image without the need for extra polygons. Our Brick and Rock materials are great examples of this. In the brick walls you can see the grout looks inset compared to the brick. This is due to the Normal Map.
If you watch the materials videos above you will learn a lot of key concepts, tips and tricks that will allow you to get the most out of your models and textures!
Good luck and if you have any questions feel free to ask!
Thank you!
Tim