How important are templates for a blogger

Not all templates cost money.

Depends on the niche I would say. While it is true that google looks for the content, visitors see much more.

I would compare it to studies done on places. The best colors for a dining area for example are oranges-reds. They will make you hungry supposedly. And restaurant owners know if they buy a specific kind of chair, the customer will be comfortable just long enough to eat and will not want to lounge there after for a long time b/c after 45 minutes they will begin feeling discomfort sitting there. Over all goal? Get them in, make them hungry, and get them out so you can seat another round of people.

This can be compared to the template - pleasing enough when you arrive, but not too distracting to take away from your content or sales pitch or what ever it is you have going on there.

I know most marketers tend to choose blue - there are advantages to placement on the blog too. For instance, if you are using a 2 column blog, your links should be on the right and your content on the left - if your content is where you want the focus to start that is. Studies have shown people look at the left side of the page first.

In an effort to do everything you can it doesn't hurt to split test. The look of a site I believe can be very important.

what's the goal?

If it's to look professional then a more professional theme would do good.

If it's conversions to sales then split testing smaller changes like the last poster said would be better

Yes, the design is very important because it will help to catch the read attention.