I make some money via Adsense. I do have some tips... no secret though - only common sense. "i need a mentor or a guide to help me work with adsense and create group of sites or bloge with good income" IMO, the number one mistake with making money via Adsense is people tend to go too fast in creating sites. I once created dozens of sites only making a few dollars a month, and then the sites tumbling one by one. The best tactic is to choose the right niche (read: topic, industry or category), build a site, nurture it well in SEO and traffic then if the site gains enough traction, you can move on to the next site. I agree with DP users saying that niche selection is the key. Yes - you are right: webmaster-related sites won't get you many clicks. Even if you did, the income per click would be very low - SEO, Webmaster, Web Hosting, etc. is niches to avoid if you want to make money via Adsense. And yes, in AdSense, traffic = income, regardless the traffic origin (SE traffic/organic traffic is cool, but it's not everything!) My 2 cents.
I think if you should start writing about VMWares or Virtualisation of Applications or Servers for Industry Level Servers to Run Applications on a VM hardware or "How To" using linux to make your simple PC. Such industry level keywords can lead serious people to click high paying ads by Linux Industrial Grade Service Providers. Using proper keywords you can have a success story There no Linux Administrator have time to earn from Online Earning Programs like Adsense. Experts have to manage there networks or Linux systems or developing there already installed systems with new Sources. I am not much familiar with Linux but yeah for my Wireless Projects I was to do lot of research work on Linux Distros and I also clicked so many Adsense Attractive ads on those sites for more and more information about the Linux and its Applications. An other opportunity could be about Video Kind of site witch required high speed broadband connection and efficiently managed Linux Servers. Select a Project And keep doing hardwork until you start earning a breakpoint for your livings.
Also try to relate the long tail keywords with these main keywords. Like a user searching for a Linux Wireless Management you can attract him by using a tile and post data about that. While creating your content think like visitors what visitors would be interested in and searching for on Google, Yahoo, Bing. Create blog for experimental base if you have 3 or 5$/month then lead to a web.