Content is King, SEO is Queen. Design is like a prince. Content is what brings people to your site, not design. That doesn't mean you should not address your design at some point, but I would stress to start out with a simple design, and focus on content. When you bring in a couple sales, start working on a design and track everything to see what helps convert.
I'm not saying structure isn't important, but people come to your site because of content, not because of your design. In other words, all aspects of a website need some attention, but Content is #1.
Content by far. I've tested ugly looking blogs with great content against professional looking blogs with average content - the better content always converts best. I'm a big fan of minimalist looking blogs, you don't need all the bells and whistles.