The look and feel of your store is completely controlled by your WordPress theme. We already noticed that even a theme like Storefront already delivers good results. It's just better to use a theme that has been created with using WooCommerce in mind. If you would use a standard WordPress theme like Twenty Fifteen or Twenty Sixteen WooCommerce will still work, but layout issues might occur.
We have two possibilities when choosing a design for our store:
To start with the first option, creating a theme ourselves is not something we could do overnight. It requires extensive knowledge of Web design, WordPress, WooCommerce, PHP, HTML, and CSS, Just to name a few. But maybe, if we wanted to have a unique design that no other shop is using, this could still be a good choice. It just requires more time and a large budget to do so. Creating your own WordPress or WooCommerce theme is a learning experience if you never did it before.
The alternative is using a standard theme. These are themes optimized for WooCommerce and available out of the box. Using a standard theme you can start right away. Some of them are even free, like for instance the good Storefront theme. We'll often find that we need a commercial theme though. Commercial or Premium themes can be found in price ranges from $20 to $200, where the majority of the themes will be offered below $100. If we had a small budget this would definitely be the way to go, since there are hundreds of themes to choose from. Remember that it's always possible to make adjustments on these themes, so that the theme of your choice better fits your needs.
If you decided to use a standard theme you'll face a new challenge: which theme will fit your needs? There are free themes available on the market, but most WooCommerce themes are commercial themes you'll have to pay for. Often they are referred to as Premium themes. These themes are supported by the developer and deliver lots of functions in most cases. That's not always a good thing though. Functionality should be provided by plugins and not within the theme itself. Besides that, having too much functions will just slow down your website. As a beginner this is sometimes difficult to judge. Just pick what you really need and do not go for the theme that offers the most functions. Look for themes that make it easy to customize the layout, colors and fonts. There are a number of resources available online to look for WooCommerce-compatible themes:

The image below shows the Integrity theme demo created using the X-theme, one of the many versatile and flexible WooCommerce themes at ThemeForest.com:

Sometimes, you may find free themes as well. The best resources are WooThemes and the WordPress.org website: http://wordpress.org/themes/. Search for WooCommerce if you're searching on WordPress.org. All themes can be used, but using a theme built for WooCommerce often gives better results out of the box. Be careful building your business on a free theme. Although it seems tempting if you're on a low budget, free themes are often not updated or supported. If there's any free theme we can really recommend, then it would be the Storefront theme, that is also used in this book. It is well written, and a good starting point if you want to learn WooCommerce theme development yourself. It is supported by WooThemes as well, which is an important asset for a free theme.
I also wrote a roundup of free WooCommerce themes on my blog. If you need to limit yourself to free themes, you should check it out. You may find it here:
http://www.joomblocks.com/best-free-woocommerce-themes-2015.
If you're not yet very familiar with working with different WordPress themes, then the following guidelines may be helpful to come to a good choice:

There are a lot of things that we have to pay attention to when buying a WooCommerce theme. However, when creating a theme from scratch, we need to pay attention to some of these topics as well. In this case, we must have, or gather, the knowledge to be able to build it correctly.