Is a paid plugin the best option for an affordable SEO boost or would I be better off having my host do the SEO or a private company?

Sorry in advance if this is a really basic question, but I made and managed a website for a relative and their SEO is not too great. We've currently been using the free version of Yoast SEO but lately I've been wondering if the paid version is worth the money or if we'd be better off adding the DreamHost SEO toolkit (our host) for $5 a month? Or a different approach? The DreamHost SEO toolkit says this: Improve your search engine rankings and drive more customers to your website with do-it-yourself tools, insights, and a personalized step-by-step SEO plan. Comprehensive Website Audit Personalized SEO Plan with Tasks Weekly & Monthly Progress Reports On-Page Optimization Tools Track Up to 20 Keywords Track up to 4 Competitors