You should choose a simple and clean template. Gmail works well with templates that are mobile-friendly. You can try using Google's built-in templates. These are easy to customize and look professional. You should also explore third-party options like Stripo or BeePro. These platforms offer beautiful templates that integrate with Gmail. Your template should focus on readability and visual appeal. You need to use a responsive design for better user experience. It's important to pick a template with clear call-to-action buttons. Lastly, you should test your template on different devices before sending.