Generate more insights from your domains to better analyze website performance.
Plan and prepare a concept of why you want to track multiple domains or packs of websites.
Create a spreadsheet of the types of data you want to analyze across all of your domains. Include whether you can aggregate all data in your Google Analytics account, the exact information you want to track, and the value this will bring to your business.
Create multiple properties for each domain you are tracking in Google Tag Manager.
Analyze each website property individually and create data sets for Analysis, Test, and Backup.
Add Google Tag Manager to your site and add the Google Analytics tag to start the basic GA tracking.
Add GTM tags for each action people take on your website - respectively the actions you defined in your tracking concept.
Create the same tags across all domains. If all websites contain similar content, add the same container across all your domains, but if the websites are significantly different, use a separate container for each.
Create 5-7 custom alerts in Google Analytics by clicking on Reports > Customization > Custom Alerts > Manager Custom Alerts > New Alert.
Use alerts that will help you maintain the functioning of your domains such as No Data, Transaction Drop/Increase, and Revenue Drop/Increase.
Export the reports in a spreadsheet and compare the data outside of Google Analytics, Google Data Studio or Google BigQuery.
Create graphs and compare data points to identify similarities in domains from the same area or that target the same niche products. With Google Spreadsheet and the Schedule & Send Email Add-on for Google Sheets you have the advantage that you can create reports or dashboards in Google Sheets and automatically send it to the inbox of your boss or customers without any further work.