That depends on what you want to do next. Do you wish to be in academics? or do you want to work? An MBA is a master's degree that is suppose to enhance your business administration skills. Many UG students pursue it after a couple of years of experience. However, there is no requirement as such. You can pursue it as a fresh graduate too. You can pursue PhD in the area of specialisation, but do so only if you are interested in getting into academics. Having a PhD wouln't add much in terms of a job in management.
The following are the options available for the same:-
1)Chartered Financial Analyst (CFA)
2)Financial Risk Manager (FRM)
3)Certified Information Systems Auditor (CISA)
4)Certification in Risk Management Assurance(CRMA)
5)Certified in Production and Inventory Management(CPIM)
6)Project Management Professional(PMP)
7)Second MBA from an International Business School
Hope this helps.