Paid ads should be your last step in marketing your range of affiliate products. You want to make sure you’re in a money-making niche and have a roster of products proven to sell, as well as proven sales funnel that compels your prospects to buy. That way when you invest the money in a paid ad, which can cost hundreds and thousands of dollars, you’ll see a decent return on investment.
For example, if I talk about how cool a product is, and then you find out that I’m an affiliate for them, wouldn’t you as a conscientious observer become skeptical as to whether my information is biased, if perhaps I’m only saying how cool something is because I can get paid for it? Wouldn’t that make you question my integrity with other things I say as well?