What plugins do you need? It really depends on what you’re trying to do: every plugin should have a job. Here are some plugins that are a good place to start:
What you get: Lots of options to turn on here but I especially like the spell check on posts, the webstats (in the wordpress dashboard) and their sharing options.
What you get: For me the biggest thing is the broad security features that protect your site. It also optimizes your files so your site runs faster. The paid version has a firewall but if you go that route I’d actually recommend Sucuri instead (plus W3 Total Cache for optimizing website speed if you are not using Cloudflare). Note: if you’re using WP Engine for web hosting you can skip this.
What you get: One click back-ups! Note: if you’re using WP Engine for web hosting you can skip this.
What you get: The only SEO you really need (good content will take you the rest of the way.)
What you get: If you’re going to allow comments, this is required. It’ll squash your comment spam before it takes over!