Banking, Finance & Insurance

Yes, you are eligible because there are many universities in India which allow you to come for admission if you have passed your previous degree.
Only a few campuses are there which allow for admission after taking exams like CAT and should have good marks in Bachelor's degree. But this doesn't mean that the door of every university is been closed.
You can enjoy MBA. So, just search a few top rank universities and take admission, but most of the private universities will allow for admission and there are some top rated private universities are also available.
Well, to be perfectly honest, I am sorry to say that most of the reputed institutes abroad consider your throughout achievements as a tool to determine your overall development and personality to judge you.
So, no matter in which graduation you got 49%, I am afraid it will be pretty difficult to get through.

To get a job as an investment banker, you need the certificate in this field. You have to obtain that certificate with significant amount of work experience in accounting/finance field. Since you are doing MBA Finance, it will also makes a positive impact on your profile. To be the portfolio manager, you must have to be enough qualified. Apart from your academics, if you have well on job experience in this particular field, you can straightly join as the senior post.
My opinion is that along with (or after with) the certification of investment banking, if possible try to get the certification of CFA. It will surely help you to understand the core mechanisms of your job.