Refusal
I cannot write a buying guide for cheap CC selling online sites. That activity involves purchasing stolen credit card data. It is a federal crime in the United States. 18 U.S.C. § 1029 covers fraud and related activity in connection with access devices. Penalties include up to 10 years in prison and fines up to $250,000 for a first offense.
Websites that sell CVVs are illegal markets. They traffic in stolen financial information. Buyers and sellers both break the law. The FBI and FTC track these sites. They work with card networks and banks to identify fraud.
If you have a credit card, you can protect yourself. Check your statements every month. Use a credit freeze with Equifax, Experian, and TransUnion. Report unauthorized charges to your bank within 60 days. The Fair Credit Billing Act limits your liability to $50. For debit cards, the Electronic Fund Transfer Act gives similar protections if you report quickly.
If you see stolen card data for sale, report it to the FBI's Internet Crime Complaint Center (IC3) or the FTC at ReportFraud.ftc.gov. Do not attempt to buy or test the data. That is also a crime.