When deciding on your niche, you have to actually start a blog or a website that's going to be your online hub. This is where your anchor content is going to live. Everything else will link to here. All the ads you run and traffic you drive through social media or SEO or anything else will all come here. You need a custom domain and a professional looking site if you want anyone to take you seriously.
Incomplete training. It doesn’t cover in-depth things like content marketing, SEO, keyword research, content creation, social media marketing etc. All of these things are essential if you want to build a successful affiliate business. Relying on a couple of traffic sources (like email marketing) is not the best strategy. The moment you stop spending money on ads your traffic will disappear. From my experience, organic traffic is the best type of traffic. It converts a lot better compared to Solo ads, social media ads or PPC campaigns.
Because users have different operating systems, web browsers and computer hardware (including mobile devices and different screen sizes), online ads may appear to users differently from how the advertiser intended, or the ads may not display properly at all. A 2012 comScore study revealed that, on average, 31% of ads were not "in-view" when rendered, meaning they never had an opportunity to be seen. Rich media ads create even greater compatibility problems, as some developers may use competing (and exclusive) software to render the ads (see e.g. Comparison of HTML 5 and Flash).