Improve the default sorting by adding 'best sellers' and 'newest' options. This module also allows admin to enable or disable these options and the default ones in the back-office.
Clone this module in your app/code folder, or install it module composer. Once installed, you'll have access to a new section 'Advanced Sorting' in the 'catalog' tab in the configuration page. You add from there the 'best sellers' and 'newest' options to the sort options of the products pages. You'll also be able to disable each of the default options included in the sort.