I agree with hipcat on this one, affiliate marketing. It's probably the best way to learn online marketing and make money in the future as your efforts start to pay off. It will take time and a lot of effort - but you can do it. There are so many guides, tutorials and gurus out there. Stick with the basics - social media marketing, content creation and build a brand from there.
With that brand and audience you build, start to 'naturally' recommend products your audience is looking for. For example, if you're writing about pets, you can easily recommend the best barking collars, or the best pet carriers, or the best products for getting rid of worms or fleas, etc. It's information the audience needs, and its a product that you can recommend without looking like spam.
Asking wrong question as bit like asking how to win on horse races as professionals make money. The question you need to ask is how you can market your own business as you get good at that you could do marketing for others.