[frivolity]

^I'm not familiar with the job market practices in Greece, nor am I familiar with your personal circumstances, but as a guy who up to two months ago was unemployed before finding something close to my dream job, I would say that it's usually not a good idea to go for postgraduate education within a year or two of completing an undergraduate degree if it is done purely in the hope that it would bring better entry-level opportunities.

While postgraduate education generally will not have a negative impact on your job search, it is also unlikely to be the key factor that wins you a good position. It would be better to focus more on the other aspects of your application that are preventing you from landing that job.

Imo, further education should only be pursued if you:
1. wish to make a career change to a completely different industry;
2. are transitioning to a mid-level or higher managerial position; or
3. are passionate about going into academia.