Well, adding a divider between the posts makes it more clear and gives orderly look. Here is the snippet to add a divider between the posts skipping the last post.
if (($wp_query->current_post + 1) < ($wp_query->post_count)) {
echo '<div class="post-item-divider">Post Divider</div>';
}
In the above code, we are adding condition if the current post + 1 is lesser than the number of the post count then we are simply printing the divider.