I am a fresh Science Graduate.

My aim is just to do CSS and become a CSP.

Now come the real complication about what should I do now?

Either should I choose my optionals and start preparing myself as better as I can to appear in CE-2016 or 2017 or should I get Masters degree first then starting preparation for CSS Exams.

According to my own, I should choose my optionals and start preparing myself along with taking Private M.A exams in the same subjects.

My optionals are Indo-Pak History/Political Science, Philosophy, International Relations & Public Administration.

Suggestions of seniors will be really appreciated.

Thanks in anticipation.

Start your masters degree, in this way you will get strong grip in one of your optional as well . and as you will be appearing in CE16,or CE17. You have plenty of time. Along with masters degree start preparing CE as well.
Masters doesn't require 6 hours University and 6 hours study at home on every day of the year. Just spare 2 hours initially for CE. Read Dawn and start building your skills of writing and English language .

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Somewhere Beyond Right and Wrong, There is a Garden. I'll meet you there :Rumi

Husseych

Doing private M.A is fruitful or I should get regular based study in any university?

I am planning to get through B.A Exams in 2015, M.A Exams in 2016 and then prepare myself for CE-2017.

It depends on you. You can go for private route if you think you have the aptitude . But remember, if you never studied private before then it may be a problem for you.
I myself feel happy with private studies, In coming August, I will be completing my professional qualification (ACCA) and B.A . Both of them I did with self study. and next I am planning private M.A economics along with job and CE preparation. Because I feel much comfortable while self studying, and I feel like wasting time and money while going to any college.

So I'd suggest you to analyse your self and then decide. If you are not very good in the subject you want to study in masters then you must attend university, But if the subject is of your interest and you have good background in it then self studying might be better option.

Give as much time to CE as you wish but remember one thing, your first priority must be Masters ,as CSS is matter of luck along with hard work .

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Somewhere Beyond Right and Wrong, There is a Garden. I'll meet you there :Rumi

Private study is not a big deal for me. I am good at it.

Doing Masters for the sake of job is not a dream for me. I just wanna be CSP and all I study is only for this destination.

Everyone says that ''CSS is a matter of luck'' but I couldn't understand this.

Being able and determined is something which is required to do CSS and nothing else.