The Power of Advertising < more formal for a title

Since  your nearly fluent I removed any words that I could to make this sound more natural.
The words left in are not wrong, but just less natural.

One of the key characteristics of the 21st century is consumerism. From the fascinating billboards to the colorful ads on magazine pages, as well as amusing slogans on televisions programs, all of them are serve one goal:  To calling out the needs (desires) within a person. I couldn’t agree more that the real needs of the society are blurred by the strong influence of modern day advertising.   My reasons are two-folds.

Firstly, along with the economic boomed in the beginning of this century, came the idea of the advertisement. Before that, people shopped only for daily necessities; and grocery stores were the only kind of shops that appeared on the streets. Later on, as the development of technology grew and the media began to advertise spread frantically all over the country. It was then, the consumer goods became popular and a must to most people. The markets were filled with clothes and accessories similar to what movie stars worn on the big screen. (means "movie screen").

Secondly, after years of development, the strategies of those who created advertisements becames sophisticated yet subtle. In other words, they were not selling goods plainly and directly but instead by did so by creating an atmosphere promoting the idea of consumption, to lure ordinary people into buying something they only “thought” they needed.

         For examples, Thanksgiving and Christmas sales that begin right after summer and can continue all the way to the eve of these holidays. People who have been constantly exposed under such holiday-mood environment will be more vulnerable to buying these consumer goods.
        Nowadays I think that people nowadays buy too many things that they don't actually need. Indeed, advertising does act as an effective catalyst for increasing sales of goods; and people are greatly influenced by advertising. media.

Of course there are many ways to say what you you wanted to express here.
My corrections are merely my own way of writing what you wanted to communicate.
However, they are correct.