Depending on the language the software you want to run on this server is written, but first of all you need to secure the server which is the first layer security, installing firewalls and make sure u create virtual servers, secondly you need git, install curl, block unnecessary ports like ssh and unlock it when u want to use it, don't install any package that already exist without uninstalling the old one if you just purchased the server but if the server is already in production you need to be technically wise on updates to avoid breaking stuffs... Always backup