The third rule is such: You must be a registered member for at least 30 days and have a minimum of 50 posts before you can create your own listings in the Marketplace. The 50 posts must be LOCAL to the site you wish to post on. In other words, to post in the Android Central Marketplace, you will need 50 posts on Android Central, NOT 50 posts on the Mobile Nations network as a whole. Rapid accumulation of posts in a forum for the purpose of meeting this requirement is not acceptable.
Marketplace is a perk for community members in good standing. I'm sure you will be able to use it in future. Meanwhile why not contribute substantive discussion in some of our almost 200,000 threads.