Ad only on posts of a specific category

Yes, you can do this with AdPlugg's Section/Category targeting feature. Here's how to do it:

• Edit your AdPlugg Ad.
• Scroll down to the Targeting section and click the Page Targeting tab.
• Expand the "Section (Category) Targeting" section.
• Enter the names of the categories that you want to target (as described in the instructions below the field).

Note that as described in the on screen instructions, you will need to have your categories declared on the page either via Schema.org Article/articleSection schema or Open Graph article:section tags. If you are using WordPress, this can be easily done by installing the Yoast SEO plugin.