Site category options are an often overlooked feature to easily optimise your display network performance. Site category options allow you to exclude broad categories of websites that are prone to generate low quality traffic.

Click on a display campaign -> Display Network (tab) -> Site Category Options (at the very bottom of the page) -> +Options

By default a lot of the site categories are not excluded. Below is a more optimised settings for the site category options.

Before excluding site categories, you should run a placement report to understand which categories apply for your particular market. Depending on your market you might want to exclude even more of the categories.