You need to choose a solution based on your own budget and requirements. If you're looking for a cost-effective solution for WordPress, then we recommend going with either AffiliateWP or Easy Affiliate.
Both are excellent options, and AffiliateWP's payout services really give you the best of both worlds.
If you want more advanced features and don't mind the per transaction cost and higher fees, then ShareASale is the way to go.