The important aspect of the optional essay is to acknowledge the gaps in your application and to provide additional information to avoid lingering questions. Ideally you can point to additional education, training, volunteering or traveling that you engaged in while unemployed.
Follow your instincts. Once a full set of application materials for your initial school have been drafted, but not finalized, the application will be sent to a former admissions committee member for a one-time review, adcomm style.
The following advice should be considered within the context of your overall strategy and target business school sbut these areas are prime material for the optional essay.
Give yourself enough time to write the best one. It would be easier for the Business School to check the exact events that led to the firing. Recollect anecdotes or stories from your childhood. The first is to allow the prospective student to explain any extenuating circumstances behind less than stellar elements of their profile.
The optional essay is your chance to explain any discrepancies in your application. Lessons Learned: End the essay by explaining what these challenges have taught you and how you have grown as a person and a professional. If possible, try to highlight something that you think makes up for the limitation at your end, for example if you have a low GMAT scoretry to highlight other academic achievements to show that that alone is not representative of your academic bent and that you will be able to adjust to the demands of a rigorous academic program.