It would be best to take up a full-time Diploma if you are unable to pursue under-graduation for some reason and want to take up a job after 12th. However, if you have completed under-graduation then get a job and take up a Diploma (not full time) in the field in which you are working.
This will provide you an expertise and deeper acumen, understanding and comprehension of your work and field which will prove to be valuable for your job.