You should look at several marketplaces if you don't know what kind of NFT you would like to acquire. This will give you an idea of the prices, what is available, and how transactions are done on each platform. First, you need to determine what kind of NFT you want. This will allow you to identify the right marketplace for you. Once you have found the right marketplace for you, you should read their disclosures. You can also search for third-party information. Many of these companies are not public, so you won't be able to report financials.
More info: https://chamcha.io/markets
