I am a b.tech 3rd year student in Computer Science and want to prepare for IAS. what would be the preferable optionals for me to choose?

I have some other quiries too. Is it impossible to crack this exam without help from any coaching institute? I do not a have a good writing skill. how can i improve it myself? And please suggest me some optionals that will be easy to cope up with. and some good books to start from zero. :-) thank u