The codex.wordpress.org/ is the reference guide to self-hosting
When you want to take off the “training wheels”, have full access to your theme code and set up your own web host, check out the Codex. Think of it as the “Secrets of the WordPress Masters” and realize that WordPress is with you every step of your journey! Example: codex.wordpress.org/Child_Themes
Keep a free theme you like, then create a Child Theme with small changes
Modern programming is built on OOP, or Object Oriented Programming, and a key component is the idea of Object Inheritance. The terms are quite simple, as in Parent and Child. The Child inherits all the Parent abilities and also allows for its own individuality to function.
In terms of a theme style, the Child Style CSS lets you easily personalize those things of the Parent Style you want to change.