Mian Faizan,
Your choice of optional subjects is not appropriate because candidates are required to select optional subjects carrying a total of 600 marks and not more than that. Pure mathematics carries 200 marks, Physics again 200, Urdu 200 and Journalism 100. This becomes a total of 700 marks. So you can either drop Journalism to make it 600 marks or choose some other subjects. To get detailed information regarding optional subjects, please visit:
http://fpsc.gov.pk/icms/admin/news/related_links/Subject%20Proforma.pdf
As for starting your CSS preparations, you may start it now because the syllabus is quite extensive. So the more well prepared you are, the better your chances of succeeding.
Also, in order to get help studying, you can visit my blog: sunehram.blogspot.com. You will see articles there on various topics. You can also like my facebook page: Discourse-sunehram.blogspot.com. Here's the link:
https://www.facebook.com/pages/Discourse-sunehramblogspotcom/234691303370360?ref=br_tf
If you have any other queries, please feel free to ask.
Happy Reading!