Templates or themes are the attractive feature of your blog. The visitor will stay at your for longer time if your template will be good. Placing attractive colourfull template won't give you a traffic.
Make the template simple. I had tried lot's of templates on my blog. I always suggest simple blogger templates.Always put light color in the background. (i.e. white, light blue., light yellow etc.)
You can give dark colour to your links, matching with the background.
75% of blogger use their blog to earn some bucks. So they require lot's of traffic. For that purpose template can't do anything for you. Your content should be unique and powerful. so that it will get ranking in search engines [Google, MSN, Yahoo etc.]