Search engine optimization (SEO) campaigns generate organic traffic. The goal of SEO is to improve website ranking for relevant keywords. You want your website to show up on the first page of organic search results – ‘organic’ refers to the middle section of results you see in search engines – for what you’re selling, and you’d probably be considered super human if you did that without organic SEO.
Each paid ad will likely point to a product page, a specific landing page, or something that has the potential to drive financial results. As paid marketing would suggest by its name alone, you’re spending money on ads to drive specific actions. You need to determine ROAS beyond vanity metrics alone (like engagement or total leads). Say you drove five leads but spent $5,000 on your paid campaign. Your ROAS would be $1,000 per lead, which is a bit steep (depending on your industry). In this case, you’d want to adjust your strategy to avoid wasting money.
When used correctly, PPC can be highly efficient. Since you only pay when people click and you can target people looking for specific terms, it can be an excellent means of bringing people to your site. Even more importantly, PPC ads have been shown in some studies to even boost visibility and clicks, particularly if your organic result starts to slip further down the page. This can help improve brand reach and maintain a strong reputation.
A good example is Facebook Custom Audiences. Within this Facebook supports email targeting, the ability to upload customer email addresses and then target those users on Facebook with tailored ads. This lets you micro-segment based on your existing customer database. One application is customer loyalty marketing, promoting offers to existing high value users via Facebook ads.
Google claims their users click (organic) search results more often than ads, essentially rebutting the research cited above. A 2012 Google study found that 81% of ad impressions and 66% of ad clicks happen when there is no associated organic search result on the first page. Research has shown that searchers may have a bias against ads, unless the ads are relevant to the searcher's need or intent 
I still believe that Facebook and Google are great platforms to promote your business, but only if you are willing to pay. If your goal is Organic growth, I recommend looking at newer platforms such as Quora, Reddit, Snapchat, Medium, Instagram, Tumblr and similar. These are all established platforms that still offer some opportunities for organic reach, because although popular, they are nowhere near the saturation levels of Facebook and Google. You can also look at startups that you feel will become very successful in the future, take a small gamble perhaps and try to establish a strong presence there.
Look at the different search engines (sources) that drive traffic to your site to determine where you want to invest your resources. For example, if you're getting an overwhelming amount of visitors and revenue from a particular search engine, that's an obvious source of profitable traffic and an area in which you might want to make further investment; but you might also find another search engine that delivers only a few visitors, but ones who represent a very high Per Visit Value. In this latter case, you might want to increase your spend in that area to drive more of those high-value visitors to your site.
Online Marketing Challenge (OMC) is a unique opportunity for students to get real-world experience creating and executing online marketing campaigns for real nonprofits using a $10,000 USD monthly budget of in-kind Google Ads advertising credit through the Google Ad Grants program. This global academic program brings two worlds together, partnering students and nonprofits, to support digital skill development and drive positive change around the world.
Every one of those engagements can amplify a post tenfold depending on the size of their network. And really you’re educating them on, ‘Hey, when you engage with our content, you’re not only just liking the content, but you’re opening that content up to all of your network, which can ultimately help with building the business’ bottom line, getting more awareness, which in turn drives more leads, and helps move people down the funnel, they build trust when they see your name more often.’
To remain competitive on the SERPs, you need to not only have keen insight into your own marketing strategy, but also what others in your industry are doing. You need to be able to pinpoint keywords for which they rank that you are not. You also want to be able to gauge their performance, including their acquisition of Quick Answers and other special features.
Well, yes and no. Sure, you can get hit with an algorithm change or penalty that destroys all your traffic. However, if you have good people who know what they are doing, this is not likely to happen, and if it does, it is easy (in most cases) to get your visits back. Panda and Penguin are another story, but if you get hit by those it is typically not accidental.