WordPress offers tens of thousands of plugins, but one of the most essential is Jetpack. This is almost a must for every new WordPress installation, as it adds additional useful features to the system that it lacks. These are often features that are available to wordpress.com users, and this plugin is recommended by WordPress itself.
Jetpack for WordPress can offer, for example, automatic creation of a simple mobile template, traffic statistics, better site editing options, content and performance management tools, etc. One can add such an option to subscribe to new posts via email, or set up comments via social networks.
Jetpack can be downloaded and activated directly through the WordPress administration, just like other plugins.