Google Analytics is a leading tool for gaining insight into your website visitors data (location, devices and so much more). It's also really easy to start using it.
T1 is clean and simple template. It's perfect for small websites with a couple of pages.
T2 has a big image for background and boxed content blocks. It's perfect for text-heavy websites. It's responsive, retina-ready and customizable.
T3 is a clean template that shows logo and navigation on the left and content on the right. It's perfect for portfolios. It's responsive and customizable.
Google Webmaster Tools
If you want to understand and improve your website in Google Search, this is the tool you must use. It's a free offering from Google.
Bing Webmaster Tools
Curious about your website performance in Bing (Microsoft's search engine)? This is the tool you must use. It's free.