Hi Laurence,
Generally speaking its all about getting traffic either organically or through ads... and in my opinion the best approach is to adopt both... I tend to use ads first as you get instant results which you can act upon with refining sales pages, building a list etc... and over time develop organic traffic through use of SEO (on page and off page) - with focus on content marketing and gaining quality backlinks and more recently I'm putting more emphasis on social media...
Using a combined approach also has the benefit of not relying on one traffic source such as G - and with that you mitigate the risks.... In addition there are many areas where these areas cross over - most particularly is keyword research, knowing which keywords have value with respect to competition, traffic and fiscal value i.e. PPC vs. ranking on the serps...
With regards to building a list and capturing leads - I would start off with paid ads on related forums, social media e.g. FB - in otherwords figure out where your target audience hangs out... the quick results will help you with building more enduring efforts with pursuing organic means... with list building make sure to offer an incentive to join your list e.g. free bonus and to provide quality info which will build your trust and ultimately allow you to make recommendations/promotions which you can earn through....
Also video marketing is another great area to pursue with regards to traffic sources as well as guest articles on authority blogs.... There are indeed many moving parts! For me its about developing a plan of action and doing ones best to keep to it....
I hope that helps, Best of Luck!
Sid