High Prefect Drikus:
Basically, to earn the qualifications to become an Orc Raider, your level must be at least 20, and you must pass the Test of the Orc Raider.
To take the Test of the Orc Raider, go to Prefect Karukia of the Orc village He will tell you everything you need to know. If you pass the test and come back, I will change your profession. To get to the Orc village, first go to Gludio, then use a Gatekeeper.