Finding a job in the marketing field, what do employers find more important job experience or post studies?

it is more important job experience beside studies and more training that what jobs need in the marketing fields

At most, It will depend on previous experience.
We all studied and take courses, But working on the field is another thing, Specially on Sales and Marketing field.

First experience but must be supported by the study and certificate

Really depends on which side of the world we are talking about ! most likely in western companies they do appreciate experience, simply they ask you straight questions if you have done this task before or not, and how and what you did, and your references for the same, in Middle East certificates are an interview opener, companies will not even call you for the interview if you don't have certificates, it is not a rule; since I had couple of interviews which I met a real marketing professionals who have the capability to evaluate the candidates, but I simply think it is a matter of culture: he is certified then he has the needed knowledge.

experience it's very important specially in the middle east , but if you were in a interview and you provide a complete marketing solutions for the company and the business and if you're convinced them with your marketing skills, i'm 100% sure they will hire you , a lot of people know the basics in marketing and how to do ads or deal with ads agencies...
etc you are a marketer :) position your self with a different values good luck!