Since you are going to do a lot of product reviews and recommendations, you are going to have to pick a topic that you have the passion for or something you have a wide knowledge of. If your passion is not within that topic, then you are likely to lose interest eventually. Therefore, it is pertinent to choose something of your interest. You can also find content writers and reviewers from Upwork or Fiverr!
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.