We can restrict the unwanted AdSense Ads using competitive filter in AdSense Setup by specifying domain/url of the Ads.
If we want to restrict Ads of particular category then we can use Category Filter option available in Ad Review Center
Category filter can be reached from adsense Setup->adReviewCenter
It will show below detail for each Category.
% Recent Earnings
% Recent Ad Impressions
We can filter the Categories which are having low earnings but having high impressions. It will help to increase AdSense revenue. And also, it will help to show only relevant ads for our readers.