Now that you have mastered modifying a WordPress Theme you are ready to create your own. There are many ways to go about this, and it’s up to you to figure out what is best for you.
Personally, I like to use a WordPress Theme framework. My favorite is called Sage (formerly known as Roots). There are other WordPress Theme Frameworks such as Genisis, Redux, and Underscores.
The reason I like Sage is that is very extensible and allows the use of modern development tools (Composer, Ansible, Vagrant, Capistrano, etc.) to create the theme.
Check it out: Roots.io