You had your A-HA (not the famous music group from the '80s) moment.
You found the team to create it.
You decided to do it on GCP, clever choice! And you've enabled your billing and started it, bad decision.
First, you must set up a budget, then add more emails to the budget alert, and finally, send notifications to Pub/Sub and save the day.
It's a great article series by Mark Mirchandani Google Cloud Developer Advocate