Some niches are more profitable for affiliate marketing. You need to focus on the one that has higher demand and low competition. I think you need to consider health niche because there are lot of subcategories you can target over there and make money with your affiliate marketing campaign. Wellness is another niche that you can target with your affiliate marketing campaign. Business and finance is a good niche as well but the competition is a bit high. You need to engage in personal research and go deeper in order to discover the less competitive niche for the above two niches. Relationship is another place you need to check out when you want to select a niche for your affiliate marketing business.