Random ad after every second post in Genesis.

functions.php

add_action( 'genesis_after_entry', 'google_ad' );
/**
 * Insert one random ad after every second post.
 *
 * Scope: Posts page and all category archives.
 *
 * @author Sridhar Katakam
 * @link   http://sridharkatakam.com/display-random-ad-every-second-post-genesis/
 */
function google_ad() {

	if ( ! ( is_home() || is_category() ) ) {
		return;
	}

	if ( ! function_exists( 'dfads' ) ) {
		return;
	}

	global $wp_query;

	if( ($wp_query->current_post % 2) == 1 ) {
		echo dfads( 'groups=50&limit=1&orderby=random&container_class=adsense' );
	}

}

style.css

.adsense {
	margin-bottom: 60px;
}