what is the age of the site is it indexed ??
Make sure how many backlinks your competitors have. Google your keyword take sites which ranks morethan you. Put that site URL into yahoo site explorer find how many backlinks they have and try to outrank them. You need to have quality content and relevant backinks from high PR sites.
It's because of Panda.I heard your site gets evaluated on a 30 days interval now,and then google will rank you till' the next check.At the moment,try and focus on building backlinks and index them.When you get around 100 or more,you should be ranked on the first page with no problem.
I'm pretty new to google, Are there any services to rent a links for a month or two? I pay some amount of money and service automatically byues links?