Suggest English reading stuff (books/articles/stories/magazi… for language improvement.?

I am an English Trainer and I conduct short term cles (40 days) for developing spoken and written communication skills of the students. Apart from cl room learning reading, listening writing and speaking are the other mode of learning. I here focus on reading mode and I want to provide some stuff as reading exercise to the students. I get the student from all levels from extremely poor to better ones. I want to get reading stuff article in such a way that commonly suits to the students of all levels. I want the language of all stuff is simple and doesn’t have high literary standard and the articles books help the readers to develop their insight into semantics (words their different meaning and different grammatical usage etc.) and sentence structuring in all they really help learners to learn language.