The Business plan is just the name of the plan. You don’t have to have a business to use that plan. WordPress.com plans below the Business plan are all subdomains on one shared environment. Bad code on one site could affect many others hence the limits on plugins to the numerous pre-installed ones.
If you only have a personal blog could you say what it is that you wanted to do that needs a plugin, just in case there is some other workaround. https://en.support.wordpress.com/plugins/