in my view if u wanna select economics as a subject, then plz plz dont study k k dewet and m l jhingan type books, as there are so many mistakes (rather blunders) in it. (these books are banned in international islamic university and qau). so my recommendation would be to study paul samuelson (best book for begginers). for the second paper i would advice two books.
1st is "issues in pakistan economy" by akbar ( i dont remember complete name of author) (oxford university press).
2nd is the latest economic survey which is downloadable from ministry of finance government of pakistan. i think its adress is www.mof.gov.pk