If honestly you're going to ask that question, then you're not informed much. I don't mean to hammer you down, but building a payment gateway is no easy feat. There is tremendous amount of domain knowledge that goes in building one, not to mention technical know-how in keeping it robust and secure.
If you're in a 3rd world country, your best option is to use SaaS Gateways like PayON.com. You'll be up and running in no time and shave off months (if not years) of your SDLC & Money.
If you're in a 3rd world country, your best option is to use SaaS Gateways like PayON.com. You'll be up and running in no time and shave off months (if not years) of your SDLC & Money.