Masters

You are advised to appear for GATE to do M.Tech on civil engineering. Incase you are interested in technical career you may appear in MBA Entrance Examinations such CAT, XAT, MAT etc. In case you want to go abroad for PG, you may appear in GRE and GMAT.

You do your PG in that subject where you have scored the highest marks. After PG, you can go for assistant lecturer job in a government college by clearing NET or SLET. You can appear for UPSC exam or can go for research work.
Many options are available for trade and commerce.

Yes you should definitely pursue PG in English from a reputed college/institute. Please refer to the link provided below for a list of colleges which offer PG courses in English. You have a wide variety of courses to chose from a vast list of colleges.
Link: https://www.shiksha.com/humanities-social-sciences/languages/colleges/m-a-colleges-india

I would suggest you secure a good CGPA in BA economics and then apply for Masters in political economics. Many colleges require a minimum pass percentage of 55% in Bachelors and few reputed colleges also conduct entrance exams for admission into their Masters courses in economics.