but couldn't begin nor find good support ideas
Well... if you google on this topic you'll find loads of information on this topic.
A few points for this essay;
1. Advertising is powerful in changing peoples'perceptions; this may promote people to buy products with inferior quality too. (when you write give solid examples)
2. Advertising also educate people about new products. services, value addions; this helps people to be more knowledgeable and aware of latest products, services etc.