coupon/deals search engine. Some people have worked out special deals with amazon sellers to promote limited promo codes. Honey is a chrome extension that finds coupon codes.
The problem with all of that is it's highly saturated.
So, you really need to think about what your going to create content about and how is it different.
Can also be used as more of an add on for your products.
When you say you want to pursue affiliate marketing what are you picturing? Its a very broad enviroment.
It is just like ads, only you are only paid for a successful transaction.