my google ads are not relevant even though I added good quality meta tags and paid attention to seo since past 3 weeks!

3 weeks eh! almost a lifetime.

BTW you didn't seem to mention anything useful such as content

I have a mobile discussion related site..!
and added good meta-tags!

when the site/pages has been crawled & indexed by Google the ads should become relevant 3 weeks is NOT enough time.

what is meant by "crawled"?

By search engines. Google in particular

by the way if your website is a blog constant post can help.. ads is base on the content of your site..

Not the site! The content of the page

And it is not done "on the fly" it takes a little while before ads are "relavent". Try it yourself;

Put up a new page and see how long it takes for the really relavent ads to kick in.

You should check your content it should be crawled by google . Than you can get the relevant ads.

Hope you will get the answer.

Thanks

Give it some time and google will crawl it again and show relevant ads

truely agree it took almost 45 days to get me the relevant ads

You can try to use the Competitive Ad filter of the sites you don't want to show their ads.

Also, log on on Google Adsense try Ad Review Center.

The ads content are determined by Title, H1, H2 content. Just try to have relevant content in these zones and your ads will be changed.

You need to get indexed first for you to have related ads. Plus also check the content of your site.