Creating blog content is a very useful and effective way of consistently building content on a site. When creating blog posts, it's a good idea to do some keyword research to figure out what it is that your audience is interested in and searching for online. Also, be sure to research competitors, forums and social media to narrow down on topics for your blog.
There absolutely is still room for new affiliates, because there are always new products to promote and new audiences to reach. The internet is a vast place with infinite verticals to work in, so instead of just focusing on the biggest affiliate programs in a specific industry I recommend using that one as well as others (and Amazon!) to round out your affiliate offers and thus your revenue.
If my piece of content is so unique and valuable around hiking backpack recommendations, that other reputable outdoor websites are willing to link to it and build the page’s authority, then I’d have a very real opportunity to rank high in organic search for these search terms (meaning, my page will come up first when someone searches for hiking backpacks).