Are there any template you would recommend, or should I import a specific blog template from Blogger, Squarespace or Wordpress?
If you mean an online magazine.. then there are a couple of great themes by http://www.rockettheme.com/ that you can use
You can't import templates from other CMS to Joomla. You must use native Joomla templates. You can find plenty of templates free and commercial for Joomla on web. Visit bestofjoomla dot com to see a selection of main Joomla template vendors.