Best working domains in Qatar:
1- Oil and gas industries.
2-CCTVs and security.
3-Military industries.

By the way ,DO NOT COME TO QATAR without having signed a contract with good salary 8000+ the LEAST, and you must have a yearly exit visa.
The exit visa is important, because if you come to live here you won't be able to exit Qatar without your sponsor's permission .( and the lot of them won't give their employees exit visa , it's like slavery.)