PhD or research is all about finding out new concepts. Thus we provide a deeper in already existing knowledge. PhD in Social Science is very much different from that of pure sciences, yet the goal is the same. As you know for doing research/PhD at the university level, the qualification required is PG degree. Every university has different criteria for selecting candidates.
As you know DSE, JNU, ISI, IEW, IIPA, and IIMs are the prime institutions for teaching, learning and researching in economics, management and public administration.
If you are willing to get into one of these institutions, a Master’s from IGNOU will have the same value as that from any other university. To get selected into these prestigious institutions, you will have to pass through a rigorous selection process of
Entrance
Group discussion
Personal interview
Moreover you will have to provide testimonials from your professors about your academic developments.
Getting admission to MIT, Harvard or Stanford can be possible from ISI Delhi. It has a very good Economics Unit. However, the same cannot be said about ISI Kolkata and also MSQE, for that matter. Do not expect to get into MIT or Harvard or Stanford by studying in ISI Kolkata.
It goes without saying that you will have to have and maintain an excellent academic record to even be considered for admission to the institutes you aspire to study in. And you also must have a good reference with the faculty so that they can write letters of recommendation for you.
One of my cousins who did a Ph.D. said that choosing a college clearly depends upon the area of interest you have in mind for the research.
Therefore, you need to choose wisely, pursuing Ph.D. would only be good if you receive a good piece of advice from your professors or someone who has appropriate experience.
IIM Bangalore is the better option for a PhD in Economics. They have an excellent Economics department. The faculty members actively pursue research projects. Many of the faculty members recently published their papers in the Journal of Economic Theory. IIM Bangalore is especially good for applied Economics. The institute has a vibrant research culture and an excellent faculty base.