To add ads at the bottom of the posts, you can add ad content space. A good way would be to widgetize it and use Widget Logic to control what ad appears on what page, etc.
So, add this to your functions.php file.
[php]genesis_register_sidebar(array(
'name'=>'Ad Content',
'description' => 'Place widgets here to fill the ad content area that appears after posts.',
));
function add_ad_content() { ?>
<div class="ad_content">
<?php if (!dynamic_sidebar('Ad Content')) : ?>
<h3><?php _e("Ad Content Area", 'genesis'); ?></h3>
<p><?php _e("This is a widgeted area designed to hold ad content.", 'genesis'); ?></p>
<?php endif; ?>
</div><!-- end .homepage_content -->
<?php }
add_action ('genesis_after_post_content','add_ad_content');[/php]