the posts push everything together

For something in between two posts:
got to wp-content/themes/tandil/style.css
and add this:

.separationline
{
	color: #000080;
	border-top: 1px dotted #000;
	margin: 0 5px;
	padding: 0px 0;
}

next in your index.php (also in your theme folder) add this:

<div class="separationline"></div>

below the existing: php the_content so that it looks like this:

<?php the_content('<span class="moretext">(Read more...)</span>'); ?>
			<div class="separationline"></div>

For more space within one post between the paragrahs:
go to wp-content/themes/tandil/style.css open the file and find:

.post p {
margin:2px 10px 5px 12px;
padding:1px;
}

and change the padding to 8px or anything you like