The trend at present is for flat design, responsive, so that viewers can use the site on any of their devices.
There are several themes, some based on Bootstrap framework, some on Genesis, but all are really easy to customise and you will be surprised at how many variations can be achieved with one theme.
My (current) favourite is OnePress, a free theme from WP. I have been designing a website for a holiday park and it looks great in that theme.
Because your aim is to sell, then you need to be sure that your chosen theme is compatible with the ecommerce plugin you will use. To that end, you may find themes made by the ecommerce plugin developers that fit perfectly together.
Good luck with your venture.
Hope you find this answer helpful.