What can I do to improve my odds of obtaining a job in the advertising world?

In support to what Jonathan said, 'Advertising' is pretty broad and there is no 1 ideal job position for it. You wouldn't necessarily want to be today's 'Don Draper'. 1- I would suggest that you start with personality assessment of yourself to know your strengths, then find the field in Advertising that need individuals with your strengths. (Try an MBTI test or Strength Finder by Gallup).   2- Then try freelancing for a period of 6 months just so that you know what customers are asking from you (marketing plan, writing copy, analyze competitions' campaigns, media plan, pitching a campaign idea, creative management in brainstorming sessions, etc). You will find out what tasks you are good at and which ones you do enjoy doing. 3 - Learn to work with people. By working with suppliers and clients you would mold into an employable team-player.  Advertising agency roles are highly interdependent. Learning the responsibilities and value each member brings respect to the workplace. At an advertising agency it really helps to be likeable (most of the time). 4 - Not all of your peers who majored in Advertising with you are necessarily working in an ad agency. Give your old classmates a call and see what they did while you were having your MBA. Its vital to know your current job market's demand for someone of your credentials.

What rank is your MBA program? Did you make use of your career center and alumni network at the school? Try those resources. You can also try to network through LinkedIn.