Modern Responsive SEO WordPress Site

I am putting together a corporate-style WordPress site that will serve primarily as a business showcase. What I need is a clean, modern build that remains lightning-fast, fully responsive on every device, and engineered with on-page SEO best practices from day one... (Budget: $15 - $25 USD, Jobs: CMS, CSS, Google PageSpeed Insights, HTML, JavaScript, SEO, Web Design, Web Development, Website Design, WordPress)