Alexa Rank ?

Alexa Ranking totally depends on your niche. Blogs with SEO niche tends to have high alexa rank with low traffic, because their visitors are mostly webmasters with alexa toolbar installed in their browser. Other blog niches will have variation in alexa ranking based on their incoming traffic. Few sites will have 100000 visitors per month, but the alexa ranking will be very low like above 100K. Gaming, medical, pharma niche are the best example.

If you want to increase your alexa rate, install alexa widget in your site and ask some one to review about your site with alexa toolbar installed in thier PC. Don't use black hat technique. Work hard to drive traffic which is the proven method to increase Alexa traffic.