What are the steps to becoming a bank approved payment gateway system. I assume you need to start with a certified server on a unique IP. Then what? Do you need to set up a handshake with the banks the same way you set up a handshake with the gateway?
What country are you located in? Assuming you are trying to setup a US payment gateway (Authorize.net) and not a 3rd Party Processor (Paypal or 2checkout.com). It would be a massive undertaking in both cost and technical requirements, but this is roughly what must happen. Generally, you need to set up an agreement with a processing platform. In the US, the largest are FDR Omaha, FDR Nashville, Paymentech, Global, and Vital. There are many more but these would cover about 85% of merchants in the US. International, you would have Pago, Moneris, and probably a few more very proprietary ones. You would create an application to integrate with these platforms. Each platform is unique, and would require completely independent integration, certification, testing, etc... You would need to have at least your own server (most likely a bank of them) on a very strong network. You must become PA-DSS compliant - https://www.pcisecuritystandards.org/security_standards/pa_dss.shtml. Security is essential, but throughput is equally important from a usability perspective.