When starting out with WordPress, if you are looking to test how to use the program, I always advise going for OCEANWP, it is completely free and comes with an unbelievable amount of customisation. I personally have used it with great results, and it is perfect for an information / small eCommerce site.
When you are looking to build something a bit more complicated or want a a bespoke feel, a premium theme can be bought from envato
Above is a link through to all premium themes. As you scroll through the market, you can click on any theme and preview it. Once you have bought the theme, you can then install it through your WordPress and have the exact same data on your site – which you can then change. The benefits here is that you can have a fully functioning site in the matter of minutes.