AdSense does not specify the exact number of articles to post before your account is approved but to be safe, make sure the articles posted are at least 30.
It’s impossible to get approved if your blog does not have enough content. One of the conditions for approval is that all your articles should have enough text—the text should occupy more space than images. Enough text means 500 words and above per post.
One thing you’ll not be told is that each article should contain more than 500 words.
For easy approval, ensure that at least 4 posts contain upwards of 2,000 words each. More than 5 articles should contain 1,000 words and above and the rest at least 500 words.
One major mistake to avoid is posting all the articles in a single or a couple of days. Some people create a site like today, they post 30 articles tomorrow and apply for AdSense the same day. My friend, your site won’t be approved. If you create a site today, make sure it’s at least 3 weeks old before making the application. The posting of articles should be spaced evenly—post 2-4 articles per day.
If possible, wait until the total number of articles are 50 before officially applying for approval—your account will be approved with ease.
Blogs with articles which contain less than 300 words are rejected. AdSense takes seriously the length of articles.
If you make a mistake of lifting articles from other blogs and making them look like yours, you will get disappointed-AdSense won’t accept your website.