I acquire websites myself as a high return investment but with...

I acquire websites myself as a high return investment but with semi-active management and technical skills required.  So I have background knowledge to see how a website's tracking day to day.

I checked SEMRush.com to see if any of the websites are increasing their free SEO traffic or their ads.  WarCom is the only one that seems to have improved recently (http://www.semrush.com/au/info/warcom.com.au).

So to my question:

Q1. How much does each website contribute to revenue?  If WarCom was a significant percentage, the improvement could have a significant impact, but from that I can tell, it's not that big.

WowBaby looks tiny according to SEMRush.  Reading the WowBaby acquisition announcement, it seemed that they didn't even care about traffic or revenue.

So that leaves maybe 2 websites generating the bulk of revenue, but not improving traffic-wise.

I was hoping to buy so I could learn something from the regular announcements and my research, but I can't justify the purchase if I can't see any growth.

Another question:

Q2. is Google free and Google ads the main source of traffic?  I thought there might be more to it, like product search engines, but Alexa seemed to think Google is almost the only source of traffic for every website.