Description meta tags are important because Google might use them as snippets for your pages. Note that we say "might" because Google may choose to use a relevant section of your page's visible text if it does a good job of matching up with a user's query. Adding description meta tags to each of your pages is always a good practice in case Google cannot find a good selection of text to use in the snippet. The Webmaster Central Blog has informative posts on improving snippets with better description meta tags18 and better snippets for your users19. We also have a handy Help Center article on how to create good titles and snippets20.
By now, you've likely seen all the "gurus" in your Facebook feed. Some of them are more popular than others. What you'll notice is that the ads you see that have the highest views and engagement are normally the most successful. Use a site like Similar Web to study those ads and see what they're doing. Join their lists and embed yourself in their funnels. That's an important part of the process so that you can replicate and reverse engineer what the most successful marketers are doing.