If you can get access to a core vocab board this has helped immensely in my room and I would strongly recommend to increase language!
You can read more about my circle time folder here and pick up some other great freebies.
Check out these great morning work binders from Ashton at the Special Education Station.
The next three things take a lot of time to prep and I would suggest starting to do once the school year starts and this won't happen all in the first year. The next three things have taken me at least four years to slowly create. I have created as I went depending on the students' needs and in priority of what is needed the most for my group of students.
You can find some social stories here.
You can find lots of adapted books here.
Well, I think those are all of my Must-Haves. What are some things you can't live without?!