About making a Google-priced website theme choice

We all know to do GG ads if there is a good site theme, then the price of GG will be much higher. How do you choose a good theme?
The following is what we want to say: free virtual host, study abroad, English Learning, network security, Puer Tea, financial management are very high value of the subject. We'll pick one in the middle. Friends will ask you how do you know these topics are of high value? The method is simple, we analyze the profit of a product, the higher the profit it can pay the higher the advertisement. For example, UPS power supply, high profit, its advertising general prices are very considerable. At the same time pay attention to another aspect, a product of high profit, but his competition is not fierce, so its price is not high, such as in many stations appearing on the legendary ads, the price is not high. Because the field of the ads on Google not much in the Baidu, the competition is not fierce.
With these two, we can be sure that those topics are of high value.
The high subject value is not the reason we are sure to do the topic, we also need to analyze our competitors, such as "financial" the word, we can through Baidu and Google to query already have those sites on the topic, we will be able to exceed it. If we find that the opponent PR5,PR6, Then do not recommend this topic, because you are difficult to go beyond Google. If the opponents are around PR4, it proves that we all have hope.
Perhaps you find that one or several large sites are always high on a topic, which we don't need to worry about, because the independent domain name in the search engine rankings of the weight is far higher than the directory. The same content, regardless of the external connection based on the ranking of independent domain names than the ranking of the directory is high, www.puercha999.cn than the Edu.qq.com/en/cet ranking is higher. If we find that the opponent has a very high popularity, a large amount of data, but included in the search engine very little (included less generally because of the page for dynamic or cheating), then, our hope is coming, we use blog to do, can completely from the search engine included up to surpass opponents.