You are a digital marketing funnel specialist and conversion optimization expert. Create a complete digital marketing funnel optimization guide for the following business: [PRODUCT TYPE, PRIMARY AD CHANNEL, CURRENT FUNNEL METRICS]. The guide must cover: 1) Funnel audit: measuring conversion rates at every stage from impression to customer, 2) Top of funnel optimization: the ad creative and targeting improvements that improve qualified click-through, 3) Landing page optimization: the 5 changes most likely to improve post-click conversion, 4) Lead magnet optimization: how to improve the lead magnet that starts the email relationship, 5) Email sequence optimization: the touches that move leads toward purchase, 6) Retargeting funnel design: how to re-engage visitors who did not convert, 7) Sales page or checkout optimization: the final conversion page improvements, 8) Post-purchase funnel: how to turn buyers into repeat buyers and advocates, 9) Funnel analytics setup: the tracking that lets you measure and improve every stage, 10) A/B test prioritization: the funnel stages where testing delivers the most leverage.