Yes, you need to build links to your site to acquire more PageRank, or Google ‘juice’ – or what we now call domain authority or trust. Google is a link-based search engine – it does not quite understand ‘good’ or ‘quality’ content – but it does understand ‘popular’ content. It can also usually identify poor, or THIN CONTENT – and it penalises your site for that – or – at least – it takes away the traffic you once had with an algorithm change. Google doesn’t like calling actions the take a ‘penalty’ – it doesn’t look good. They blame your ranking drops on their engineers getting better at identifying quality content or links, or the inverse – low-quality content and unnatural links. If they do take action your site for paid links – they call this a ‘Manual Action’ and you will get notified about it in Google Search Console if you sign up.
If you are using Responsive Web Design, use meta name="viewport" tag to tell the browser how to adjust the content. If you use Dynamic Serving, use the Vary HTTP header to signal your changes depending on the user-agent. If you are using separate URLs, signal the relationship between two URLs by tag with rel="canonical" and rel="alternate" elements.

If you have a commenting system (like Drupal, Joomla or WordPress) that allows for search engine friendly links (commonly called dofollow links) from your blog or site, you will probably, eventually be the target of lots of spam, be complicated in tiered link schemes and potentially fall foul of Google’s webmaster guidelines on using the attribute in certain situations.

Google, in many instances, would rather send long-tail search traffic, like users using mobile VOICE SEARCH, for instance, to high-quality pages ABOUT a concept/topic that explains relationships and connections between relevant sub-topics FIRST, rather than to only send that traffic to low-quality pages just because they have the exact phrase on the page.
Today, however, SEM is used to refer exclusively to paid search. According to Search Engine Land, Search Engine Marketing is “the process of gaining website traffic by purchasing ads on search engines.” Search Engine Optimization, on the other hand, is defined as “the process of getting traffic from free, organic, editorial or natural search results.”
QUOTE: “Over time, we’ve seen sites try to maximize their “search footprint” without adding clear, unique value. These doorway campaigns manifest themselves as pages on a site, as a number of domains, or a combination thereof. To improve the quality of search results for our users, we’ll soon launch a ranking adjustment to better address these types of pages. Sites with large and well-established doorway campaigns might see a broad impact from this change.” Google, 2015
Inclusion in Google's search results is free and easy; you don't even need to submit your site to Google. Google is a fully automated search engine that uses web crawlers to explore the web constantly, looking for sites to add to our index. In fact, the vast majority of sites listed in our results aren't manually submitted for inclusion, but found and added automatically when we crawl the web. Learn how Google discovers, crawls, and serves web pages.3

QUOTE: “As the Googlebot does not see [the text in the] the images directly, we generally concentrate on the information provided in the “alt” attribute. Feel free to supplement the “alt” attribute with “title” and other attributes if they provide value to your users! So for example, if you have an image of a puppy (these seem popular at the moment ) playing with a ball, you could use something like “My puppy Betsy playing with a bowling ball” as the alt-attribute for the image. If you also have a link around the image, pointing a large version of the same photo, you could use “View this image in high-resolution” as the title attribute for the link.” John Mueller, Google 2008
QUOTE: “For instance, we would see a lot of low-quality posts in a forum. We would index those low-quality pages. And we’d also see a lot of really high-quality posts, with good discussions, good information on those pages. And our algorithms would be kind of stuck in a situation with, well, there’s a lot of low-quality content here, but there’s also a lot of high-quality content here. So how should we evaluate the site overall? And usually, what happens is, our algorithms kind of find some middle ground……. what you’d need to do to, kind of, move a step forward, is really try to find a way to analyze the quality of your content, and to make sure that the high-quality content is indexed and that the lower-quality content doesn’t get indexed by default.” John Mueller, Google 2014
I think the anchor text links in internal navigation is still valuable – but keep it natural. Google needs links to find and help categorise your pages. Don’t underestimate the value of a clever internal link keyword-rich architecture and be sure to understand for instance how many words Google counts in a link, but don’t overdo it. Too many links on a page could be seen as a poor user experience. Avoid lots of hidden links in your template navigation.
When Googlebot crawls a page, it should see the page the same way an average user does15. For optimal rendering and indexing, always allow Googlebot access to the JavaScript, CSS, and image files used by your website. If your site's robots.txt file disallows crawling of these assets, it directly harms how well our algorithms render and index your content. This can result in suboptimal rankings.
While it is possible to see results from your marketing efforts quickly, the reality is that marketing, especially the type that generates long-term results and referrals, takes time. You're competing in an increasingly crowded and loud marketplace. The better you can connect with your ideal market and develop a relationship with it, the better your results will be. If you provide a great product or service and are attentive to your customers, your customers will provide you with positive reviews, referrals, and testimonials that will help you stand out in the crowd.
Link text is the visible text inside a link. This text tells users and Google something about the page you're linking to. Links on your page may be internal—pointing to other pages on your site—or external—leading to content on other sites. In either of these cases, the better your anchor text is, the easier it is for users to navigate and for Google to understand what the page you're linking to is about.
While SEOs can provide clients with valuable services, some unethical SEOs have given the industry a black eye by using overly aggressive marketing efforts and attempting to manipulate search engine results in unfair ways. Practices that violate our guidelines may result in a negative adjustment of your site's presence in Google, or even the removal of your site from our index.