Here is a good way to track external links and image banners in Google Analytics using Google Tag Manager: https://www.absentdata.com/track-external-links/
In the illustration, it is using Just Links; in our case, we are using All Elements, as we want to track the banner images as well.
Here might be another page to help you out for the variables you need to implement: https://www.zoomowl.com/link-click-tracking-using-googleanalytics/
You can check it Realtime > Events and should get something like this:
Let me know if it works for you.