Restore Google Visibility On-Page SEO

My site has slipped out of Google’s results and I want it back where users can find it. The issue looks confined to on-page SEO, so I need someone to inspect every element that influences how Google reads and ranks each page... (Budget: $30 - $250 USD, Jobs: Content Strategy, Content Writing, Internet Marketing, Keyword Research, Link Building, SEO, SEO Auditing, SEO Writing)