When I first started to grasp what LLMs could actually do, I wondered what would be possible if I could customise the GPT to understand a specific context (e.g. my business). At the time, this was only possible with complex custom setups. But that changed when Open AI released the ability to create Custom GPTs in ChatGPT. Once this capability unlocked, I already knew the use case I wanted to try first. And the results were a genuine game-changer.

Marketing without marketing skills

I’m completely clueless when it comes to sales and marketing. If someone tested my sales skills, here’s how it would go…

Me: Do you want to buy this pen?

Them: No

Me: Ok, fine

My business, Freely, needed an email lead nurture sequence. Between my wife and I (both co-founders of Freely), we knew the key points we wanted to convey and how we wanted customers to feel when they read the emails. But bringing this to life as a sequence of emails, each with a catchy title, value proposition and call to action… wow, what a challenge.

Without the Custom GPT that I built specifically to help us with this challenge, it would have taken months to personally upskill enough to produce the result that we achieved.

Creating a Custom GPT

I use Chat GPT, which has the concept of a Custom GPT. But, if you’re using a different platform, it might be called something different like Projects, if you’re using Claude.

The first challenge was giving it enough context to deeply understand my business. I didn’t want generic advice, I wanted the AI to understand who we are, our values, what we’re trying to achieve, and what’s important to our customers.

Creating the knowledge files

I took a concept I learned about on the AI Explored Podcast and tailored it to my needs. With the help of ChatGPT itself, I created the following files…

  • The Business - Outlines the company’s purpose, mission, vision, target market, products, and strategic goals. Establishes the “why” behind Freely and articulates what makes Freely Homeschool Planner unique in the market.
  • Customer Personas - Provides detailed, emotional, and behavioral insights into core customer personas. This is explained in more detail in this post
  • Marketing Plan - Outlines the target audience, emotional drivers, pain points, and messaging strategy for Freely, with detailed plans for content distribution across platforms. It also addresses common objections and risks in the sales funnel.
  • Content Guidelines - A comprehensive guide for creating content using the brand’s voice. Includes a repeatable storytelling framework, tone guidelines, channel-specific adaptations, and strategies to nurture audience connection and drive engagement.
  • Product Features - Outlines the capabilities and benefits of Freely Homeschool Planner in detail.
  • Content Examples - Real examples of high-performing blog content.

Writing the instructions

I always use a Prompt Engineering GPT to improve my instructions. That way I can just do a bit of a brain dump, and it will turn it into something robust and comprehensive. Here’s what I provided…

I need a prompt to create a custom GPT that is an expert in email marketing to assist with my business. I will provide it details of my business, marketing plan and customer avatars as knowledge files. I want this email marketing expert to be well versed in setting up complex email sequences that blends emails based on the customers sign up date and time sensitive emails (e.g. based on the current time of year) that provide value to both leads and existing customers. They need to have expertise in emotive copywriting that builds trust, educates the user about their problems, provides value for free and demonstrates authority. They also need to know how to write copy focused on conversion by addressing risks and objections and positioning the business as a strong and worthy solution to the customers pain points

Then I simply checked the output (which was clear, well-structured, and on point), copied and pasted it into the instructions for the new custom GPT, and uploaded the knowledge files.

Using the Custom GPT

Once I created a GPT that truly understood my business—our tone of voice, audience mindset, product strengths, and goals—it became a genuine creative partner. Over several sessions, it helped me not just write emails, but design a complete lead nurture experience that felt cohesive, human, and true to our mission.

This was the first time I felt like I wasn’t just talking to AI, we were collaborating, together

Mapping the journey

We began by looking at the structure and purpose of the entire sequence—not just writing individual emails, but defining how each one fit into a larger flow.

Together, we mapped out a four-email journey that:

  • Introduced Freely’s values and voice in a welcoming, personal tone
  • Built trust through empathy and shared struggles
  • Helped readers reframe their challenges
  • Positioned Freely as a solution to these challenges

Each email had its own purpose, with a distinct call to action that gently moved the reader forward.

Refining the wording, structure & presentation

We worked iteratively on each draft. The GPT helped me:

  • Improve flow between sections and tighten up repetitive copy
  • Reframe value propositions in line with our brand voice
  • Rewrite feature blurbs to highlight their value to the customer
  • Break up dense text with headers, white space and colour
  • Maintain consistency in tone across the sequence

Subject lines and preview text

The GPT also helped develop subject lines and preview text options that balanced:

  • Curiosity without clickbait
  • Emotional resonance without manipulation
  • Visual interest (using selective emojis)
  • Clarity of benefit

It gave me A/B test-ready options for each email—paired sets of subject lines and preview snippets that felt aligned with each email’s intent.

The end result

By the end of the process, I had a fully polished, emotionally grounded lead nurture sequence that:

  • Was deeply aligned with our mission and customer mindset
  • Provided immediate value and support
  • Introduced Freely in a natural, helpful way
  • Used CTAs that felt like invitations, not pressure

This was the first Custom GPT “team member”, but it certainly wasn’t the last. I’ve gone on to build over a dozen more to help with various challenges across other areas of marketing, advertising, UX and strategy.

If you’ve got questions, ideas, or just want to compare notes, I’d love to hear from you! Feel free to reach out on LinkedIn or via email.