You are about to complete you BSc- Economics, you also want to have a masters in economics and opting for a teaching career.
A.Most of us would be in a dilemma as to what to do next when we are about to complete one degree. There is nothing wrong in this, the best way forward depends on your age, financial status, and the urgency to start earning soon. Important would be what you and your family feel about your profession as a teaching faculty. If you are sure about this and going to apply for a government job, then you need to take up B.Ed.
Because for any of the government teachers competitive exams, you will need a minimum graduate degree AND a B.Ed.
B.I would suggest, join for the B.Ed course in a reputed Government or a deemed university as a regular student and study sincerely and perform well.
C.Once you start you B.Ed, please enroll for a distance education course of MA/MSc Economics
Indira Gandhi open unveristy and other good UGC accredited universities offer distance learning for M Sc programs, you can choose and join one (http://www.ignou.ac.in/ignou/aboutignou/school/soss/programmes/detail/120/2)
D.If you clear your exams in time, you will have a BSc, B.Ed and a M.A/MSc ecnomics.
Based on the results you can consider writing the TGT/PGT exams for recruitment as teachers in government education departments. You can also consider taking the NET exams in Economics that will give you the eligibility to start working as lecutrer in Government or private colleges.
E. Once you find and start a job as a lecturer/faculty member in the department of economics, as you gain teaching experience and be in line for promotions, you can focus on doing your Ph.D. in Economics via IGNOU or other UGC recognized universities.(http://www.ignou.ac.in/ignou/aboutignou/school/soss/programmes/detail/93/2). This would enable you to be prepared for promotions to professor level in the same or a different college.
F. This would be the basic plan for the future that would suit your situation, you can always keep an open mind to fine tune it or modify based on a change of circumstances and opportunities in the future.