The chances are that if you sign up with a broker affiliate program you’ll be promoting forex and CFDs. Most brokers in the forex industry offer their currency pairs as CFDs. Usually, they will also offer cryptos stocks, commodities, indices, ETFs and bonds as CFDs. It’s more a question of understanding your target audience and adjusting your message to suit them. You may choose to focus on forex, or you may promote CFDs - whatever you think will drive traffic. Forex traders can be more aggressive and easier to convert.