If you've done masters in IR, then these are brilliant subjects to chose. I have prepared gender studies and History of Pakistan and India so can give a more personal review of these two. History of Pakistan and india can seem intimidating because of the timespan but most of the later portion of it overlaps with Pak studies and the rulers from 712-1857 we've all either heard about or the events are vaguely familiar at first glance. It was a mildly tedious subject to cover but highly satisfying once I was done with it. Gender studies is easy, fun and interesting to cover.

I think the key point here is that don't give much thought to "scoring trends". Pick subjects which you want to study and would genuinely enjoy giving a good portion of your time to. CSS is a relative exam. So you aren't being judged by some set standard but basically by the papers the examiners have checked before you. If in relation to them you've done well (even if it would be considered fairly avergae on its own), you can score well. And conversely if some exceptional papers went before you then even if your paper is above average the scoring would be a little more stingier. When lots of people opt for a subject in an year it is said to be "targeted" by the examiners when in fact there is a fairly good chance that amongst the large number of hopefuls are people who've either done nasters in that particular subject or just did exceptionally well and hence are now the standard (as compared to a normal year when a couple of dozen people chose a subject and no one really knows much about it so everyone can get by on average). I hope this makes sense. This isn't meant to demoralise you but give you a fairly clear view of the expectations. I wish you the very very best of luck.

I would like to give you a word of advice which I wish someone had told me sooner. Before starting a subject create a word document. Take the time to go through the past five year papers of the subject and copy the questions into the document. Then try to sort them into groups. For example for Gender studies there are topic on gender studies as a subject (its relevancy and importance), history of feminism, feminism in Pakistan etc. You'd notice that each subject can be whittled down to a few main topics. They rarely repeat questions in css but the general points stay the say each year. This is really helpful because the syllabus given for many of the subjects are really all-encompassing and broad. So when you start preparing from the syllabus and go through its topics you can have the word document open with you to see what kind of questions come and how to frame your studies. The word document would also come in handy when you finish up a subject but are still unsure whether you've grasped enough of it. You can give yourself a self-set quiz from the previous questions to see how well you would do. This could apply equally as well in the compulsory subjects (esp general sceince and islamiat) as with the optional ones.

Anyway wish you the best of luck once more. I hope you found this helpful.