As someone working in a specialized PIL area and with somewhat high-level work exp. in IL, it is quite difficult to break into a career in international law (especially outside India). Let me put this through my own experience in somewhat realistic terms:

1. The first issue is that the PIL core taught in India is often really inadequate. When you try to launch yourself in a PIL career, you come to realize the sheer competence gap that exists between what you are taught and what you need to know/understand/apply when a task is handed to you. Yes, IL mooting will help you bridge that gap but then again these moot problems are merely enactment of "semi-fictional disputes" and - trust me - disputes is one of the smaller circles of PIL. My basic point is that conceptual wholeness is lacking what you are taught and moots do not help you bridge it because in narrowing down on certain IL issues, you tend to lose sight of actual policy issues due to which these "disputes" may never actually arise. . Law schools focusing on dispute resolution is natural but to imbibe the idea that IL is about disputes is odd. But then again, that's my own view.

2. Academia v. non-Academia. IL careers that often get highlighted are academic ones. If you can get over the conceptual hurdles in the first issue then academia is a good area of work in IL - and depending on your stars you may land a job outside or can even come back and teach in India. But a certain level of expertise is needed when you are seeking a career in the academy or outside. Outside, the work is either State-oriented work (you supply competence and advice to States on disputes, negotiations) or non-State work (working with law firms, IGs, NGOs etc.). But all this is a question of competence (and if you are thinking of working abroad, of course, visa). To gain a foothold in these work areas you need to have a credible standing which at early stages is a product of work experience or your higher studies. IL studies in India will usually not prepare you for this work (maybe SAU might? no idea)

3. Competence. You might be catching the main point of this answer here because this is the biggest issue in my view. You have to build your competence in this area. IL has gotten increasingly specialized over the years and - in my view - will continue to get even more specialized. The onus is double for Indian students looking for IL careers: they have to master the conceptual basics (which you did not get at LLB levels) and then you also have to garner a degree of specialization to differentiate yourself from not only your Indian peers but also those from world over. Only then are you "competitively" there in terms of a career in IL.

4. Luck. Cannot stress on this enough. IL careers - especially in State-oriented work and IOs and IGs - is all about luck. Even if you reach the level of competence I outlined above, when you apply, things depend very highly on chance.

5. You mentioned work experience. Prior work experience is pretty much standard now I believe. It is extremely rare (at least now) for me to have found someone who made their career in IL without having a considerable degree of work experience in IL (be it in negotiations, policy, disputes etc.). But the worry is how do you even go about finding good work experience in IL? There is no one doing "only IL" work in India. (If they are, its often unpaid). And then again, if you are gaining work experience in Indian IL setups, the rate at which you develop competence might be slow if you simply rely on their work to teach you. That way working in IL in India is also a challenge because much of the time you are building your competence on your own (making mistakes and learning, which is time-taking).

6. LLM/Masters. Yes, you can simply go for a masters and get it all over with an LLM degree but that's not the same thing I feel. Everyone says that "work experience matters for your LLM applications" but rarely do they explain what that even means. It orients not only your application but it shows that you have a degree of understanding in the subject matter - not to the colleges but to your prospective employers. So yes, you can directly do an LLM, general or specialist, and look for jobs but you will be in a job market where people have had years long worth of work experience in State-oriented work or non-state. That puts you in a situation you perhaps didn't want to be in but that's another issue. Which is why when you say "careers in IL", I want to mention that work experience ought to be valued above any degree. Smallest of work experiences matter but the bigger the better.

Above all that however, learn on the go. Learn from the people you work under, paid or unpaid. Don't think they'll teach you IL like Mr. Salve sits and talks about one case at the ICJ but pick up on their attributes. Pick up how they tackled their career trajectory. Use that experience.

7. Satisfaction, pay and comfort. My own idea of PIL work is that it is really satisfying. The moving parts of the global political economy is split open right in front of your eyes and you are engaged in stretching your bandwidth to grasp it all. (It is, however, tough to estimate what impact your work has/will have) But it is extremely satisfying to work in this field.

Pay. The bugbear (?) of all nascent IL careers. You can count on one hand the number of IOs which pay their interns. From that you can understand how much unpaid work goes on in this field. But that's the price of the field nowadays. Once you break in, however, it gets better I believe. State-work pays depending on the level and, of course, the country you work with. Being Indian doesn't necessarily mean that you have to work with India only. Smaller nations often pick up people who are available and of proven competence. IOs and IGOs come with smarter pays, better career plans but yes, your work might get less exciting and your career may not progress meaningfully.

But hey! you made a career out of it, didn't you? If you want things to be perpetually be exciting then negotiations is your playground. Advising and negotiating on behalf of States is thrilling stuff. But such posts are a combination of the things I have talked about earlier: vacancy, competence, and (of course) luck!

Hope this gives some insights. As mountainously difficult as it looks, its perhaps still doable if you work towards figuring it all out. This is all the clarity I have today but some time back even I was asking the same questions. I know I might have missed out on things that you probably wanted answers to but I am happy to take any follow-up questions.

Depends on what "worth it" means to you. There are several trajectories, I outline some below:

1. Academia - it is getting more and more niche, as in all things: so you may want to think of a specialisation. You need to have a top academic record, and do a good job on your doctorate. Some Indians have done exceedingly well in this sphere, for example Lavanya Rajamani is an established leader.

2. Bar/Arbitration/Advocacy in a disputes context - Incredibly difficult, as mentioned in another comment. The best bet may be to either qualify at the English Bar and choose an international law focussed set (but many times, this involves doing commercial work as well: the Bar/disputes firms tends to have people who do commercial as well as investment arbitrations); and then some may choose to focus on public international law related issues. But this is over a career of 4 decades; you will become a "PIL barrister" only in the last decade... The other option of going down this route is to join a PIL focussed firm (Volterra Fietta etc.) but there would be very limited vacancies and getting in is very much a matter of luck/timing.

3. IOs and Consultancy - tied to academia: if you want to go down this route, getting there through the academic route is probably the way to do it. Again: in terms of role models - Priya Pillai is someone whose career you might want to study.

4. "Niche" practice involving international law: The main area is (other than BIT arbitrations and then leading on to public intl. law arbitration/Hague) seems to be international tax. But beware: it is only at the leading edge of this practice area that you get your real PIL interface. You need to be at the absolute top of your game - otherwise, you will end up as a tax lawyer only connected in a very ancillary manner to PIL (you will cite VCLT a few times a year!) than do any deep PIL work. But at the top edge - you can really advance the frontiers of international tax by applying hardcore PIL concepts. Philip Baker is at the forefront - Porus Kaka is one of the very few Indians in the top league in this area. There are also tax focussed IOs (OECD, for instance) which do important work. Tax is an especially interesting case study for PIL lawyers in terms of expanding notions of jurisdiction in tax, etc. Lots going on at the moment. But you need to have a really deep interest in tax law, rather than just PIL.

In any event, if you are young and/or have time to explore, you might want to do a well regarded postgrad degree, a doctorate under a renowned supervisor, and also do things like Summer Courses at Hague, apply for judicial clerkships with international tribunals, think of working as arbitral secretaries, and then figure out which of the routes works best.

Is it worth it? Really depends on the opportunity cost and on the intrinsic worth to you of working on PIL.

Finding a career in PIL is incredibly difficult, even abroad. If you think Senior Counsels and Magic Circle firms are an Old Boys' Club, its more so at the PIL bar. UK students find it hard to break into Hague, so you can only imagine how hard it is for Indians. A top UK/US LLM is barely a foot in the door.