Christina Johnson: How to Waste Less Money on Digital Marketing

Christina Johnson has been shown a 33x return on ad spend and kept a straight face. She has sat with a retail media network selling hundreds of millions of dollars in advertising whose own sales team couldn't explain to buyers whether the money had worked. And she can point to a supplier that ran a flawless campaign in cities where the retailer has no stores.

Christina Johnson spent years inside Walmart's retail media business before founding Advisar, an intelligence tool for retail media buyers. In this conversation, she and Noah break down why so many brands are flying blind on their ad spend, why a metric like ROAS can look great while sales go nowhere, and what happens when AI gives you a confident, completely wrong answer.

If your business runs any kind of performance marketing, this episode will change how you look at your own numbers.

You'll hear:

• Why more ad spend rarely means better marketing
• How a "perfect" campaign can drive zero real sales
• What questions to ask before trusting a marketing metric
• Why AI can be confidently wrong, and how to catch it

Timestamps:
(00:00) More ad spend doesn't mean better marketing

(00:55) Meet Christina Johnson, founder of Advisar

(03:34) Why retail media is "wildly backwards"

(09:10) The meeting where the sales team couldn't explain their own numbers

(10:51) The question every retail marketer should ask

(12:24) The auto-bid campaign that spent $0 and sold nothing

(13:43) Why Christina built Advisar

(15:50) The "33x ROAS" that wasn't real

(18:46) ROAS explained, and why it can lie to you

(19:45) Using Claude for analysis, and where it breaks

(34:26) The AI mistake that changed how she builds

(41:08) One thing to do tomorrow with your ad spend data

Resources:

Valet — Episode Sponsor

Valet is the founding sponsor of the Serious People Podcast.

AI is getting very good at making useful things: dashboards, analyses, internal websites, and small tools. Making those things available to the rest of a team is a separate problem.

Valet lets you publish AI-created artifacts to a stable URL. New sites are private by default, and members of your organization can access them after signing in.

Try Valet at https://valet.dev

Christina Johnson operator field guide: https://seriouspeople.valet.run/spp-christina-operator-field-guide

Connect with Christina on LinkedIn: https://www.linkedin.com/in/christina-w-johnson

Advisars Website: https://www.advisar.io/

Connect with Noah on LinkedIn: https://www.linkedin.com/in/noahlevin/

Noah’s Website: https://www.noahlevin.com/

Serious People Website: https://seriouspeople.ai/

• (00:00) - More ad spend doesn't mean better marketing
• (00:55) - Meet Christina Johnson, founder of Advisar
• (03:34) - Why retail media is "wildly backwards"
• (09:10) - The meeting where the sales team couldn't explain their own numbers
• (10:51) - The question every retail marketer should ask
• (12:24) - The auto-bid campaign that spent $0 and sold nothing
• (13:43) - Why Christina built Advisar
• (15:50) - The "33x ROAS" that wasn't real
• (18:46) - ROAS explained, and why it can lie to you
• (19:45) - Using Claude for analysis, and where it breaks
• (34:26) - The AI mistake that changed how she builds
• (41:08) - One thing to do tomorrow with your ad spend data