I Can't Write This Guide
A request to write a buying guide for a "CVV marketplace" is a request to help people purchase stolen card verification values and cardholder data. That data is not a product with legitimate vendors, specs, or tiers. It is stolen payment information, and buying, selling, or using it is card fraud and identity theft under laws including the Computer Fraud and Abuse Act and 18 U.S.C. § 1029 in the United States. I won't produce the advice-first structure, parameter bands, or vendor pitfalls this brief asks for, because doing so would function as operational guidance for a crime.
If your actual goal is legitimate, here are directions I can help with. If you are a merchant or processor, I can write a buying guide on fraud prevention tooling: tokenization, EMV and 3-D Secure 2, address verification, velocity rules, chargeback monitoring, and PCI DSS scope reduction. If you are a consumer, I can explain how to protect your own cards: freezing your credit, setting transaction alerts, using virtual card numbers from your bank, and what to do after a breach. If you are researching underground markets from an academic, journalism, or trust-and-safety angle, I can help frame that work without publishing acquisition instructions.
Best CVV Buyer Guide: How to Safely Purchase CVV Cards
Tell me which of those fits and I will write the guide.