Whether you're selling B2B or B2C is also going to make a big difference here.
Our main channels getting started were Google and a review site called Capterra (did paid advertising on both), as well as LinkedIn Marketing. Now we have a few other channels and partnerships but that's how the company got off the ground and profitable (I say we to refer to myself and my business partner)
The conversion rates for AdWords (Google) and LinkedIn campaigns are going to be different because the ads are (or should) be different.
On Google, people are searching for a solution, so your ads should promote your product/service. On LinkedIn, people are just browsing so it's more effective to promote a helpful resource (eg, a guide or whitepaper).
[0] http://www.gkogan.co/blog/the-complete-guide-to-getting-sale...
Good information and nice illustrations.
For your illustrations, do you use pen and watercolor?
I use pen and water-based markers (Prismacolors); they look like watercolors but are much easier and cleaner to handle.
It looks "classy".