The best way to write an essay like this is to take one or more advertisements and try to analyze them. This will be much more simple than trying to talk about all advertising as a whole.
Look in magazines or newspapers or perhaps look at TV ads (though you would have to describe these in your paper, which is less effective than being able to attach an actual ad to your essay). Once you have found ads that work for you, look at them carefully. How much information are they giving you? Is there anything about the quality of the product? Anything about its price or what makes it a good product? What images is the ad using to try to persuade you or manipulate you?
When looking at that question, be sure to think about the use of sexuality and of wealth. In other words, is the ad trying to tell you you'll be more desireable or will look richer and more cultured if you use it?
If you do this, your essay should be easier to structure and to write.