Student or Learner
When a new student comes to you to learn English, how do you start teaching him and with what grammar topic?
The first things anyone wants / needs to know are survival phrases to help them get along in daily life. These are the things that are usually in the first chapter of just about any book on learning a new language. Things like "Where is..." Hello, excuse me, and all that stuff.
After that, I generally teach my students a lot of nouns so that they can name the things in their world. When it comes time to put together grammar and things to speak and write whole sentences, I begin with present tense verbs (but not modals like can and might) and pronouns. "I eat lunch. He goes to the store. I read a book."
When they're competent (roughly) I teach them how to manipulate syntax to create negative phrases. This also means teaching the words Do / don't and Does / doesn't which don't translate into some languages.
After that, I teach them to put the Do / don't and Does / doesn't in the front of the sentence or put the To Be word (am, is, are) in front of the sentence to create questions.
That should take up more than a few classes. I hope that helps.