I have the same question. Just that I have a master in IR. So I am confused if I should choose political science for both CSS and PMS or opt for IR in CSS and Pol. Science for PMs?
Plus I need guidance about the rest of the two subjects for PMs as well.
The subjects combination I have initially in mind for CSS is the same as yours.
"International Relations, International Law, History of USA, Gender Studies and Sociology"

Since it's an old thread, I am hoping that you have found the answer and can guide me about it as well. Thanks.
I would really appreciate it if other seniors on this forum guide me about it.
Many thanks.