Hey Jan, glad it made you think. As you've found out it's not easy to rank #1 on Google especially when so few people will link to your product reviews. You need to tackle a specific niche with a focused target audience as a whole and build a community of like minded people around your site in order to make any significant income online sustainably and for the long term.
It’s important to know where your traffic is coming from and the demographics of your audience. This will allow you to customize your messaging so that you can provide the best affiliate product recommendations. You shouldn’t just focus on the vertical you’re in, but on the traffic sources and audience that’s visiting your site. Traffic sources may include organic, paid, social media, referral, display, email, or direct traffic. You can view traffic source data in Google Analytics to view things such as time on page, bounce rate, geo location, age, gender, time of day, devices (mobile vs. desktop), and more so that you can focus your effort on the highest converting traffic. This analytics data is crucial to making informed decisions, increasing your conversion rates, and making more affiliate sales.
You should also make sure you aren't competing with your own affiliates for eyeballs. Any marketing channels you're using, such as search engines, content sites or e-mail lists, should be off limits to your affiliates. Put marketing restrictions into your affiliate agreement and notify partners immediately. It's your program--you set the rules. Or, if you prefer, you can let your affiliates run the majority of your internet marketing.