Well, you have to invest some time then to get better idea about subject combinations and their marking trendings. First go the syllabus uploaded on fpsc website, after going through sylabbus then come on this website and check all subjects indivudually to have a better idea. Everyone has different aptitude and preferences for subjects, so go for subjects you find interesting and easy rather than relying on other's choice and preferences. After all this, then you will be in a better position to get better guidance from seniors which can be to the point and productive for you .