First and foremost, you’ll need to optimize your website, that’s the biggest issue usually! After that you can turn your attention to your droplet.
Since you are asking about your droplet, here are a few steps. Since you are using cPanel with PHP-FPM, I’ll recommend switching your mpm to mpm_event. It’s the best as far as I’m concerned. It can be changed from your EasyApache configuration in cPanel.
Additionally, you’ll need to install a module in cPanel for httpd2. This again is installed from your EasyApache configurations. Don’t forget to add OPcache as well, it works really good with mpm_event and httpd2.
I’ll recommend updating your PHP version to at least 7.2 as well, 5.6 is really old and as it’s older it’s slower.
All of the above should help you with optimizing your droplet however, you can take a look at installing redis as well.