In my opinion, if you want to run WordPress, your server needs at least PHP 5.2. 4. However, by now the official recommendation is that you run PHP 7 or higher (the current version is PHP 7.1). That's because, just like WordPress, new versions of PHP bring a lot of improvements with them. Moreover, if you are a beginner in this domain, I can help you. There are many tools that make your work easier, one of them is
https://stylemixthemes.com/motors/, where you can find the best WordPress themes. Use it!