The biggest advertising accounts to watch

Hi! Welcome to the Insider Advertising daily for October 8. I'm Lauren Johnson, a senior advertising reporter at Business Insider. Subscribe here to get this newsletter in your inbox every weekday. Send me feedback or tips at ljohnson@businessinsider.com.Today's news: The biggest advertising accounts agencies are watching, Narrative's Series A pitch deck, and inside the marketing of gummy vitamins.
T-Mobile CEO Mike Sievert
Robyn Beck /AFP/Getty ImagesThe top advertising accounts agencies a