Every single person who has ever lived on this planet or will ever live on it in the future is, by definition, a unique individual, as no two people can possibly be identical. Thus, in order to write an essay on this topic, you need to think through what precisely you mean by the terms.
One way popular media, especially advertisers, misuse the term "individual", is by suggesting that buying some mass produced product or group of mass produced products owned by thousands of other people you can demonstrate "individualism," and that this is somehow a good thing.
One way to start an essay is to look at the mythology and commodification of terms such as "individual" and "unique" and ask why these are thought to be virtues. For example, if everyone else is stopping at red lights and moving at green lights, and you do the reverse, you are definitely acting in an unusual fashion -- but this is idiotic rather than good.
In your essay, you might find some examples of advertisements that use the term "individual" or "unique" and see how this term is used to persuade you to buy products.