The highest paying affiliates tend to be those who promote financial or software products. For example, credit card referrals, web hosting services, and online courses typically have commissions ranging from $50 to over $500 for each sale made. Amazon pays much less for its commissions but makes sales more easily because of the trust it has built with people. What would you like to promote first as an affiliate?
I have heard software and finance affiliates pay better than others. The web hosting, credit cards, and investment sites tend to pay better and on a per-sale basis. Amazon is beginner friendly, but the commissions are low.
It depends greatly on the niche you may want to work in. Finance and tech are some of the best paid. Yet they need confidence and experience. Amazon may pay very low compare to others, but it is quite easier to make money there.