Google AdSense is probably one of the easiest ways to make money online with a WordPress website. You can basically build a WordPress website from scratch, add content to it continually, and then add Google AdSense advertising to your posts.
I definitely know that this works as I have done this myself. I build websites as a full-time job, that not for other people, just for me to make money online. People do not believe me when I tell them what I do and I can hardly believe it myself.
If you really want to get technical when using Google AdSense, it is good to have well search engine optimized content so Google knows what adds to put on your website. It is also good to listen to what Google AdSense tells you and suggests in regards to placing your ads. For example the AdSense team sent me an e-mail suggesting some ad placements and I did it. My revenue in AdSense earnings increased by 500%. This sounds crazy but that is what happened.
The Google AdSense is not the only way of monetizing your website. There are many options available and it is better not to put all your eggs in one basket. I bet you have heard that saying before.