We have in the middle an open source time series database called InfluxDBis designed for collecting data that is timestamped such as performance metrics. Into that, we feed data from an open source project called Telegraf which can feed in more than just SQL Server statistics. And to be able to show us the data in nice pretty graphs that we can manipulate, drill-down on, and even set up alerts we display it using Grafana. Links to all of these products you find as we go through the setup of the solution.
Tracy’s post is dedicated to installation and configuration more than defining metrics, but it does get you on the road to custom metrics visualization.