We send all ticket purchases as "e-commerce" data to Google Analytics (GA). This contains data about price, orders, event names, etc.
To view E-commerce in Google Analytics you must first enable "E-commerce" in the GA property.
If you want to setup Goals then add the following as your goal destination:
/order/completed
Tip: It may also be beneficial to take a look at the presentations in this article about how to integrate your Billetto account with Google Analytics.
Important: It's important that you add the Billetto domain to your list of excluded referrers to exclude payment gateways as described in the slides.