Limit Google Ads to particular blog posts

Ultimately, Google Adsense is just a script that you insert somewhere in your html. If your theme is well widgetized, there are plenty of places where you could insert the script using the default text widget. To hide/show the widget on specific pages you could use a visibility widget (plenty of choice) that lets you specify the conditions.

If your theme doesn’t have a widget area in the place where you would like insert the ad, you could build a child theme that inserts one in the appropriate place, for instance by hooking into the featured image and display the ad after it, depending on certain conditions.