You can check ShareASale they have been in the affiliate marketing business for a long time. They have lots of products and you will mostly get all the relevant products related to your market or category.
It does not matter what the best affiliate marketing programs are, the most important thing is you. What do you like to be marketing? If you know the product or service, you will profit from it. Look for a product or service that you understand well in order to know how to market it.
Good luck For all
Join SaaS affiliate programs as they offer digital products that are in high demand also SaaS Affiliate Programs pay high commissions and also recurrent for lifetime.
For example, set up a blog about how to start a business online and promote related products and therefore earn money from the same customer for different services. Domain, Webhosting, Website Themes, Email service and Website performance monitoring like StatusCake Partners.