It is a very good idea to use different product promotion strategies so you can figure out what is working and what is not. Try to do split testing and measure the performance of each campaign then take actions accordingly. Changing a few things here and there can increase your profit dramatically. Make sure to place the banner ads on different areas of your site’s pages. Some positions will make the ads more noticeable than others.
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.
Can you make money with affiliate marketing? The short answer is yes, affiliate programs can earn a extra money and even a full-time income from home. The long answer is a little more complicated. Like any home income venture, success comes not so much from what you choose to do to make money, but whether or not you do what needs to be done correctly and consistently.