I'm not sure, it would be better to contact your own government and ask them what would make a suitable recruit. Having a good base in one or more languages may help, but in Australia, most people I know who want to work for DFAT - department of Foreign Affairs (which can mean working abroad in Aussie Embassies and working for governemnt) study 'international relations' or 'political science' both are the same thing, i believe Americans call it Political science, we call International relations. Or if your in the Middle East, maybe Middle Eastern studies, (personally if i get time, i might take some courses as electives at my university, its really interesting). Politics would help a lot. 

Hope this helps a little, it is difficult question to answer, because i'm not sure what the procedure is in your country.

good luck

For working in a diplomatic service you must be fluent in English language. it is the general qualification. But, the requared qualification and the mathod of recruitment are depend on the country. In my country Sri Lanka you should have a  university degree apply for the diplomatic mission. Then a compatative examination is hold and follow by a systamatic interview. Anyway you can achieve your target by a proper plan. I think now you in the right track as you have joined the italki to improve your English knowledge.

(5)   There   is basic philosophy to understand, and if you turn to books on the history philosophy you are going to encounter   a  nightmare of irrelevent  and mostly useless data.  What you do not do know about is:

 (A)  Platonic Dualism   which has consistently been   the tradition in  Western Civilization   for the past two millennia.   Mind/Body Dualism is the recognition that Matter, Energy, Space & Time (BODY) exists, but also that Abstract Concepts  exist only as Pure Thought in the Mind.

  Thus, Mental Objects such as Thoughts, Ideas, and Concepts exist, but as Abstract Concepts or Transcendental Concepts, and not as  Natural Phenomena.

    The World's Religions qualify as  a form of Mind/Body Dualism.

(B)   Monism  is the current challenger to  Platonic Mind/Body Dualism

   Monism is the worldview that  nothing but Natural Phenomena exists,  which means that the only realit is Matter,  Energy, Space and Time and that Science is the only credible source of data on any subject.

     This in a nutshell, is what   philosophy is all about for modern people.

  1.   Dialectical Method

  2.   Logic

  3.   As much history of the world that you can manage, but I would recommend in particular that you focus  upon  the concepts of   Roman Law   and English Common Law  and the history of

 The English Civil War (1642–1651) and the regency of Oliver Cromwell  and the beheading of King Charles I of England.

Then French Revolution 1789 until 1799   and the  subsequent  Napoleonic Wars.

Of course,   the American experiment with democracy follows.  Thomas Paine's   "Common  Sense"

and the American "Declaration of Independence"   would be other relevent literature.

   4.  I think it very instructive that you familiarize yourself with some literature on the subject of political activism such as  "Rules for Radicals" by  Saul  Alinsky.  Although  the book should not be accepted as some sort of completely true political philosophy,  the book addresses so many subjects that   play our in both the political and diplomatic sphere as to be one of the most informative texts ever written.