Should I quit my job and travel the world before applying to PhD programs?

The way PhD admission works is that you usually apply during the fall, receive admission decisions in the following winter/spring, make a decision around April and enroll in the fall. This means that there is usually a four-month(ish) long gap between the admission process and enrollment. Many students fresh out of college will use this period to relax, maybe even travel around the world. So if you can afford to quit your job or make certain arrangement with your employer, this time window could be a compromise between your need to enjoy life and appear productive, since people don't usually expect you to work hard just before you formally enroll in the program. On the other hand, if you urgently need to travel well before application and still want to impress the admission committee, my general advice is that a generic travel plan will not achieve the goal here. For your travelling to be viewed positively, it should yield concrete outcomes demonstrating excellence in whatever skills valued in your field of study.

I should also say that this is based on my experience with Ph.D. programs in science. A political science Ph.D. may have difference culture/expectations.

Adding some kind of work to your trip, that's what could make a difference for an admission committee.

Examples: Visit all or a lot of european parliaments and trial some sessions open to the public. Contact some foreign NGOs and learn about their ideas and activities. Some activities like this could even be postive for your application.

Employment is necessary to pay the rent. But you have built up some savings, so that's apparently not an issue. Whether it is or not is none of the admissions committee's business.

I haven't sat on any admissions committees, but I would think that the committee will be trying to predict, from your application, whether you seem likely to succeed in the program you're applying to. I would think that your undergraduate record, your essay and your references would take much more weight than a precise accounting of how you spent the gap between finishing the degree and submitting your application.

People take breaks from academics all the time for family and other personal reasons. It isn't necessary to explain the details when it's not a very long break. Three years would take some explaining, because some fields change quickly, and one could get rusty with some of the material and skills learned as an undergraduate.

If you enjoy writing, go for it -- but please go into it without high expectations of size of readership or income gained. Just do it for the satisfaction of writing and perhaps being read. Given the unpredictability of the success one might have as a professional writer, it would raise the stakes too much for you during your gap time to set too specific a definition of "time well spent."

Just follow your instincts, using your hunches about what would bring you personal growth, and what would help you prepare for the hard work of the PhD to come. Experiences living abroad can help you get perspective, and build your self-confidence.

(I personally would recommend that you consider picking a small number of destinations, so you can immerse yourself in a language and culture, rather than skimming the surface in a grand tour; but only you can decide what sort of itinerary would be best for you.)

Let me start with a disclaimer: I am a math professor and have no knowledge of how admissions to foreign policy PhD programs (or any other aspect of such programs) work, so take my answer with the appropriate grain of salt.

That being said, I personally think your plan is totally awesome, and am already somewhat impressed with both your desire to grow as a person and with the specific plan you have come up with for doing so. To me, your desire to learn about other cultures not from books but from actively traveling in other parts of the world speaks to a much higher level of curiosity and independent-mindedness than almost anyone I can think of who has come up with some pretentious-sounding plan for filling the year before starting grad school with some internship, work experience or other CV-padding gig. Moreover, I strongly believe that at least in the US the value of traveling abroad is seriously undervalued by most people, even within academia. My personal philosophy is that traveling (if done seriously and with the right intent, and ideally if done for extended periods of time) is far from the frivolous, hedonistic activity it is made out to be in popular perception, and can actually be a profound learning experience that changes people and their outlook on the world and even on themselves in ways they could not appreciate beforehand. So again, your plan really resonates with me personally. Now, it's quite possible I am not representative of anything or anyone, but I thought it worth stating my position in case you find it useful to know that people like me exist. After all, if I hold such views then quite possibly there are others like me who can recognize the value of what you are thinking of doing and be impressed by it. Maybe some of them will upvote my answer or weigh in in the comments section.

Now, getting to the practical question of whether your travel plan may undermine your grad school applications: I can't say with anything approaching certainty, so definitely seek advice from better informed people. One thought I have though is that if you present your plan correctly it might mitigate the effect of being technically "unemployed". For example, you hinted that you plan to write a book. Well, that by itself is a wonderful idea that is sure to make you stand out (especially if you realize the plan successfully); suddenly your trip can be not a sightseeing trip but a book-writing/research expedition, and you no longer sound so unemployed while you're doing it - see what I mean? The point is that your travel-the-world idea is actually (in this one person's opinion at least, as I said) very worthwhile, so the trick is to find a way to communicate that value in your CV, statement of purpose and other application documents. If you do that successfully, I think it's indeed quite conceivable that you will actually put yourself at an advantage rather than a disadvantage compared to other applicants. Anyway, good luck, and send us a postcard.

I don't know how admissions work in your country, so I'll leave the others to advise on that, but here's something that I learned after completing my PhD:

A PhD will put the rest of your life on hold until you complete it and pass your viva (and you better do much more than simply pass your viva).

My wife and I both got Physics PhDs, emerging out the other end practically in our thirties with no money, no house, no marriage, no kids, no relevant industrial experience. This might not be as much of an issue for you as you've already been in work.

Additionally:

A PhD is only as good as the amount of time and effort you put into it, and there is practically no ceiling to this investment.

If you want your PhD to be worth more than the certificate, you need to publish good, novel work and make yourself known to the community. If you want to be really good, your PhD will drain everything from you.

To conclude:

I would advise you to do whatever it is you want to do now, before starting your PhD, because you won't be able to justify the time away from your work during it.