what is best way to advertise the websites that i am making money on?

[Johnny B]

PPC is a waste of time and is just a con.
Free advertising also has its limits and is usually never long term and many are just for regional areas.

The best way is to add your sites into databases that get spidered by many major search engines.
Most of the best ones you'll need to pay a small fee.

You need to make sure your sites are listed in the most appropriate categories or they wont come up when people use search phrases.

Add your site to this Database:
http://www.search-the-world.com/form/listing
They have been around for many years and provided real results and offer permanent listings that you never have to add or pay for again once listed.