Grameen

Hello, everyone I am planning to apply for 2018 fall, depending on the preparation. Being cautious and nervous about my current status, so let me know there is actual possibility to apply for Ph.D. - Working for government's development agency for 5.5 years (when applying for 2018 fall) Within above working experience, work in developing country (africa region) for 2 years as a deputy director, - On-going masters degree for public policy in my home-country - B.A. in political science, 4.0/4.5 No GRE, but will take soon. Toefl 110. Questions are.. I want to change my major from Poli-sci to Development economics, and take few courses such as micro, macro, econometrics in my grad school program. How should i prepare for development economics PhD program? Is it better to get higher score on GRE instead of focusing on courses? Is there any possibility to get in top-tier (15 ranking) schools with my backgrounds? Thanks a lot