There is no hard and fast rule for finding the best template for Google Slides. However, there are a few factors that you might want to consider when choosing a template. First, think about the purpose of the presentation. There are different templates designed for different purposes, such as business presentations, academic presentations, or personal slideshows. Second, consider the Audience. Different templates are designed with different audiences in mind. For example, some templates are more formal while others are more playful. Third, take into account the length of the presentation. Some templates are better suited for shorter presentations, while others are better for longer ones. Finally, consider your own personal style and preferences. There are literally thousands of different Google Slides templates out there, so you should be able to find one that suits your needs.
Here are a few links to some popular Google Slides templates:
https://www.presentationgo.com/best-google-slides-templates/
https://www.slidescarnival.com/en/google-slides-themes
https://blog.hubspot.com/marketing/best-google-slides-templates