Lead-Source Attribution Build: GTM + Gravity Forms + GA4 + Data Studio (Multi-Site Agency)

We're a digital marketing agency managing a portfolio of client websites (WordPress + Gravity Forms + CallRail) and need to build end-to-end lead-source attribution across all of them. Right now we have no visibility into whether leads come from Google organic, Google Ads, or Google Business Profile - we want to fix that on a lead-by-lead basis and report on it month-over-month across clients. What we're trying to achieve: when a lead comes in (form submission or phone call), we know with high confidence where it came from, and we can log into a dashboard to see channel trends per client over time. Scope of work: Requirements & spec. Review our existing setup and produce a clear implementation spec to hit the tracking goals below. We've done significant groundwork (UTM schema, channel logic, persistence approach) - you'll validate, refine, and execute it, not start from zero. GTM implementation. Deploy a first-touch UTM/gclid persistence solution across sites via Google Tag Manager, so attribution survives multi-page visits (landing page → contact page) and populates form fields reliably. Gravity Forms. Configure hidden fields (utm_source, utm_medium, utm_campaign, gclid, landing_page, referrer) with reliable dynamic population across all client forms. Some sites are being standardized onto Gravity Forms. Attribution logic / automation. Build classification logic (gclid = Paid, utm_source=gbp = GBP, Google referrer no-UTM = Organic, etc.) and pipe lead data into a central table. We use Make.com - comfort there is a plus. Reporting dashboard. Build a Data Studio (Looker Studio) dashboard showing leads by channel, per client, month-over-month, from the central data source. QA & documentation. Test each attribution path end-to-end (the multi-page persistence hop especially), and document the setup so it's maintainable and repeatable across new clients. Required experience: - Google Tag Manager (custom HTML tags, triggers, dataLayer) - GA4 (custom channel groups, event/conversion config) - Gravity Forms (dynamic population, hidden fields, webhooks/notifications) - Looker Studio (multi-source dashboards, blended/aggregated reporting) - CallRail - UTM strategy and cross-channel attribution logic Nice to have: - Make.com (or similar automation) experience - Experience building attribution across a multi-site / agency portfolio To apply, please answer briefly (applications that skip these will not be considered): - How would you persist UTM/gclid values across a multi-page visit so a form on the contact page still captures the original landing-page source? Describe your approach. - Have you built attribution reporting across multiple sites/clients before? Briefly, what was the setup? - Roughly how would you approach classifying a lead as GBP vs. organic when both come from Google?