you want a list of each tag, with that tags posts below it?
here is what I have to do that, there is some other stuff going on but I’ll leave it in there. I haven’t built this site in quite a while but it should still work.
this is this page: http://ephotopros.com/tags/
{% assign sorted_tags = site.tags | sort %}
{% for tag in sorted_tags %}
{% assign vids = tag[1] | sort %}
{% if vids != empty %}
<h2 id="{{tag[0] | uri_escape | downcase}}">{{tag[0]}}</H2>
<p>
{% for p in vids %}
<a href="/{{p.type | downcase}}/"><img src="/assets/img/{{p.type | downcase}}.png" alt="{{p.type}}" title="{{p.type}}"/></a> <a href="{{ p.url }}">{{ p.title }}</a> ({{p.type}}/{{p.category}}) » <span class="entry-date"><time datetime="{{ p.date | date_to_xmlschema }}" itemprop="datePublished">{{ p.date | date: "%B %d, %Y" }}</time></span>
<br />
{% endfor %}
</p>
{% endif %}
{% endfor %}