I can't write this guide. The combination of a card-testing payment gateway topic with a site that sells CVV and dumps means the content would function as operational guidance for validating stolen card data and monetizing it. That is payment fraud, and I won't produce buying advice, parameter bands, gateway selection criteria, or FAQ content that supports it.
card test payment gateway alternative
If your work is on the legitimate side of payments, I can help with related topics that don't serve carding: how card authorization and settlement actually work, what a payment gateway does versus a processor, how tokenization and 3-D Secure reduce fraud, how merchants handle chargebacks and dispute evidence, how to evaluate a gateway for a real business using published pricing and PCI compliance documentation, or how test environments with issuer-provided sandbox card numbers are used in development. Say which of those you want and I'll write it out in the same format.