The plugins solely depend on what your website needs. As a rule of thumb, install as little number of plugins as possible, because each additional plugin slows down the website.
Most people like Contactform7 to run their contact forms, and many use Jetpack to extend a few Wordpress functions. You will probably need a Captcha plugin like ReCaptcha, and many people are using Yoast SEO. All of these have been a round for along time and can be considered "safe". But all these are purely optional, and they might not perfectly fit your needs.
When selecting a Wordpress plugin, two factors come into play: Watch out for the number of stars a plugin got (rating). Personally, I'd never even try out one that has less than four out of five stars. Also watch how many users have rated a plugin. If it is only a low number, you cannot be sure that the rating is accurate enough. Normally, plugins that have four stars or more and many ratings, e.g. >1,000, can be considered more or less "safe". Plugins with low ratings or a low number of users always pose a risk to the website's security. The same is true for themes.