The easiest solution to deploy and to display all metrics and informations about the server I have used is netdata, which can be deployed with a single command. Otherwise, solutions like Zabbix are pretty good but may require an additional server to host them.
A planned and organized strategy for maintaining actually helps a lot. As other mentioned you can monitor server live with the tools like Nagios , zabbix however there should be a routine check up too , things like checking error logs , viruses , messages , errors , disk usages etc...
A health monitor isn't necessarily going to help you optimize your server, it'll monitor core services or specified services and alert you when there's issues, essentially.
If you need to optimze your server but don't know how you should consider contacting a server management company for advise and support, most will complete optimizations for you for a relatively decent fee and will also tell you what they've done so that you can learn for the future as well.