Building a list will allow you to get repeat visitors and market to the same people over and over again.
Don't look for the short term quick cash method. Instead focus on building a long term sustainable business that creates massive value to all of your visitors and customers.
If you can do that, then you will begin to find it easy to make money online. Making money online will stop being hard and will start becoming predictable.
Don't try to reinvent the wheel. Instead focus on doing what works.