Guide on creating beautiful LaTeX documents?

Hi everyone,

I wanted to create my own document or report, and I wanted to make something that is quite custom and fun to read.

I looked at some designs online, and I am blown away away by the designs shown in this Stack Exchange!

I wanted to know how do I learn to make custom designs like that?

What libraries should I use? I want to make custom text fields and have different colours or design elements to show some underlying meaning, like definitions, warnings, error prompts, etc.

I understand that my question is kind of vague, but what's a good starting point?

Thanks! :)