This webinar aired on September 14th, 2017 with Colton Miller (Director of SEO Strategy)
With Google Analytics and Tag Manager you can see, for example, 12 people clicked here. It is the best although it isn't 100% accurate. Once you get Google Analytics they have some interaction reports you can run to essentially see what people are doing on your website.
Another thing to add to that, especially for small business clients, simply ask the customer when they reach out to you, "How did you find us?" Often it is difficult to determine that this lead and sale came from SEO efforts. It can be challenging with Google Analytics, Search Console, and other things that Colton has mentioned. You can identify and attribute revenue, but the best is simply to ask - how did you hear about us? how did you find us? That's a good indication that your online presence is strong.
In my opinion, I would say SEO is going to have the best longterm return. Hands down. You can grow it if you need to. If you are strapped for cash, with SEO you won't have the stress of spending only $50 a month on marketing like you would with PPC/Adwords. Buying a picture or two from someone, redoing content on your site, outsourcing content to free yourself up to do something else - regardless of the actions you take in SEO, they will continue to build return. Even if a blog page gets only 10 visits per month, over a time frame it will build that organic following for you. Even if something doesn't' have the most immediate results, results yield time over time. With SEO, you can grow it as you want to.Answered by Colton Miller, Director of SEO Strategy at Boostability