The type of plugins that you need will depend on the type of your WordPress website and your needs.
There're however some general plugins that all kinds of WordPress websites can benefit from.
Some of the must-have WordPress plugins include;
Yoast SEO handles all the SEO needs for your website. It is also the most used SEO WordPress plugin.
Akismet is the most popular plugin to combat spam on your blog posts and comments.
Contact Form 7
Contact Form 7 is the simple and most flexible plugin to add contact forms to your Website. All websites need some kind of forms and this plugin makes it super easy to add as my forms as you like.