The easiest way to get notified in real-time whenever a user is created in Active Directory is by forwarding “Microsoft-Windows-Security-Auditing” event 4720. This event is logged to the Security event log whenever an Active Directory user is created.
More information on event id 4720, including associated audit settings, is available on system32.eventsentry.com
Event Log: Security
Severity: Audit Success
Source: Microsoft-Windows-Security-Auditing
Category: User Account Management
Event ID: 4720