While you are using the Joomla free templates that you find, you will need to think about the design of your website. The most important thing is to make sure that your content can be read and also can be found on the internet.No matter how good the template looks, if you put in a color that clashes with the background, your website will still look bad and you will lose the potential customers or clients. This will harm your business reputation and could also damage your personal website, especially one that is gaining income from affiliate links or advertisement revenue.
You will also need to make sure that all of the information is high in SEO. There are some templates that will help with that by making the layout easy to read. However, there are some templates that will add tables and other aspects, or stop pictures from being added. This will not help with the high quality keywords and the ability to be found in the online searches.