Most of the online products have their own in-house affiliate programs. All you need to do is find the hottest selling products in your niche and take the opportunity to market these products. For example, if you run a blog about dogs, you can try to find an affiliate program related to dog food or dog care. Find the companies that are selling such products online, and on their website you will find the links to the affiliate programs. Alternatively, you can simply Google “site:domain.com affiliate” or “(product name) + affiliate program”. These are manual searches, of course, but this works in most cases, especially when you are in a niche where it is difficult to find an affiliate product. (An example of this might be something like tattoo designs.)
While it is possible to see results from your marketing efforts quickly, the reality is that marketing, especially the type that generates long-term results and referrals, takes time. You're competing in an increasingly crowded and loud marketplace. The better you can connect with your ideal market and develop a relationship with it, the better your results will be. If you provide a great product or service and are attentive to your customers, your customers will provide you with positive reviews, referrals, and testimonials that will help you stand out in the crowd.