If you are building both from scratch, build the customer narrative first. This is the opposite of what most founders do and the opposite of most fundraising advice.
The reason is that the investor narrative is downstream. Investors are underwriting whether customers will buy. If you cannot explain what a customer buys and why, you have no foundation for the claim that many of them will. Founders who polish the investor story first end up with a compelling argument about a market and a vague answer to "what do you sell."
Overwatch is the clearest version of this we have worked with. Y Combinator alum, capable team, real technology, and two years after demo day they had no revenue and investor confidence was slipping. The instinct in that position is to fix the fundraise. The actual problem was that the offer covered so much ground no buyer could tell what they were purchasing.
The work was the customer narrative. Repackaging the technology into specific, high-urgency use cases in cyber and fraud, with messaging an enterprise procurement team could act on. They landed pilots with Visa, Chase, and NASDAQ. Then they closed a $5M round.
The order matters. The customer narrative produced the traction, and the traction produced the investor narrative. It did not work the other way, and two years of trying is what proved it.
Glow showed a related version. Strong mission, no traction, and a pitch built around future vision rather than something anyone could buy today. They were trying to raise $3M with no prototype. The work was to reposition around real-world campaigns brands could understand, then resize the ask to match the evidence they actually had. They raised what they needed and landed conversations with five major brands, all of whom asked for draft contracts.