Upgrade One-Page App Landing

I have a single-page site already taking shape; I just need a skilled hand to finish it, polish every detail, and put it live. Its only purpose is product/service promotion for my digital product—an upcoming app—so the page must be tight, fast, and conversion-focused... (Budget: $30 - $250 AUD, Jobs: Graphic Design, HTML, JavaScript, PHP, SSL, Web Design, Web Development, Website Design)