The topic you choose must have enough depth that you can create a lot of content for it. This is important for building an authoritative site, for search engine optimization, and most importantly, for the end user. If you don't have enough content about a topic, you're not going to be taken very seriously as an authority on the topic and it's unlikely you can convince someone to make a purchase from you.
You can make really good commissions from the eBay partner but it depends on the products which you decide to promote. Interestingly the commission levels vary according to where you are in the world not just on the products you decide to promote. One of the great reasons to sign up is that you can earn DOUBLE commissions in your first three months. They offer free to use link generators, ad creatives and widgets for you to promote different eBay items. eBay has over 162 Million active buyers which means there is a great potential to convert your traffic.
As you probably guessed, the scale of strategies behind promoting Clickbank products is much larger than the ClickBank itself. One thing you must understand is the fact that you need to choose your strategy based on the product, not what you know. Every product has a different audience and every audience requires a different approach, that’s why if you want to become a super affiliate on Clickbank, you need to learn these different strategies and choose the right one based on what you promote.