Google is continuing to push improvement of search experience for mobile users, as the market continues to show a preference for browsing this way, so why wouldn’t Google reward sites that focus on this? Unless your market segment is dominated by desktop usage, we would suggest now taking a mobile-first approach to your web and search projects. You can use your Google Analytics account to understand on which devices most visitors come to your site, and you can split search volume trends by mobile and desktop in some search keyword research software. SEMRush is our preferred provider.
Google currently has two search indexes (mobile and desktop), but plan to combine them into one index soon, which will be responsible for crawling mobile versions of pages first, before the desktop version, so if your site doesn’t perform well on mobile devices, now’s the time to put the work in and change that, or you could find your search rankings are affected. You can use software such as Browserstack to see how mobile-friendly your site is, and Google also offers its own optimisation testing that splits desktop and mobile on PageSpeed Insights, though this has recently changed to incorporate the Chrome user experience report, and speed is no longer detectable for a lot of smaller sites.)
Make sure all elements of your site are crawlable on mobile devices – you can use Google Search Console “fetch as” tool and check that the bots can find you.