You need to become a Gold Member to apply for google adsense. Not just that, you should have participated actively in writing reviews and resources. Participating in polls or just putting queries in the forum alone will not be counted to apply for adsense. Your participation should have bought in valuable inputs to IRC.
Google is expecting atleast six months contribution in any site to get approved, However if you have enough self writtened contents you can go ahead and try to create Adsense account after three months you join IRC, if your application gets rejected for any reason, dont just simply re apply, just increase your self writtened contents and apply after atleast one month gap, else there is a chance for your account may be rejected again.
Feel free to ask me if you have more queries.
Member of IRC