Hi @ares ,
please take a look here if it helps to get started:
https://learn.microsoft.com/en-us/azure/architecture/framework/cost/monitor-alert
https://learn.microsoft.com/en-us/azure/cost-management-billing/costs/tutorial-acm-create-budgets
In the Scope
you can select the Resource Group.
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(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Andreas Baumgarten