When I was teaching high school English, I rarely used the class textbook because I found it to be big and cumbersome, and it lacked relevant, quality texts that engaged my students. So I mostly created and sought out my own resources to use. Unfortunately, that led to the predicament of arranging and organizing materials into a clear and coherent sequence for myself and my pupils. I wish I would have compiled my stuff into some kind of digital format (beyond throwing stuff on my website) to make resources more accessible and engaging for students, and to make the management side easier for me.
Below are some resources that will help guide your thinking and provide options for creating and/or customizing your own textbook. This is just a short list, but it is a good starting point: