Can I ask what age you're teaching?
I've taught just basic gerunds in elementary school, but mostly just in the form of hobbies: I like playing piano.
I can post those if that would be helpful, if you are teaching older students you could use songs with fill in the blanks. Jack Johnson's "Sitting, waiting, wishing" has great examples of different types of gerunds. You might consider using it as a warm-up, you can go through and explain the reasons gerunds are used, what else you could put there or how to transform the sentences.
eg: " I was sitting, waiting, wishing that you believed in superstitions ---> I sat, I waited, I wished that you believed in superstitions."
"Putting up with them wasn't worth never having you" -------> "I put up with them, it wasn't worth never having you."
I haven't taught it, but just a random thought.