Hey. Yes you can use just one website to promote multiple affiliate programs, but I’d say that your website should focus on just one niche. So you mention, SellHealth, that would lead me to believe your site is about health and fitness. I would then advise you to stick to that niche rather than promoting unrelated products like dog leashes and fashion accessories.
Infographics are currently an extremely popular type of media. An infographic showing information or data in an interesting and fun way can help engage an audience and generate numerous likes and shares. As infographics take more time to create than just simply uploading an image, busy website owners are prepared to pay for custom infographics. And don’t worry, an infographic can be created using simple design software such a Canva. So extensive graphic design skills are not necessary, just a creative eye.
However, like anything else truly worthwhile, apps require a significant investment of your time or money upfront. If you don't have the skills, then you have to hire someone who can assist you in creating a great app. But first you need to come up with an idea that will sell. Do the proper market research and analytics to come up with the right app.