Set up Gemini, Gem, Notebook, and Google Drive as a client assistant for a marketing agency

A Gemini account that has never seen your client’s brand guide will write generic marketing copy. The fix is not a better prompt. It is a small system: client documents in Drive, a curated NotebookLM notebook on top of them, and a Gem that knows where the facts live, how the client sounds, and where it has to stop and ask you. Setup takes an evening per client. Five prompts do the work.

What the system looks like

Most Gemini setups feel messy because they mix two things that should stay apart: what the assistant knows and how it behaves. Keep them separate, and each one becomes easy to maintain.

The Gem reads the notebook. The notebook reads Drive. You edit whichever layer actually changed, and the rest keeps working.

Step 1: Write your own standing instructions

Personal context is the box Gemini reads before every chat you open, including chats that have nothing to do with work. It holds facts about you, not about any client, so keep it under 200 words: your agency, your role, how you write, what you will and won’t claim about your work.

Don’t write it cold. Open a new Gemini chat and let it interview you.

Interview me so you can write my standing instructions for Gemini. Ask one question at a time and wait for my answer.

Cover: which agency I work at and my role there, what kind of clients we take on and what we turn down, how I write (three words, plus words I avoid), and what I can and can't claim about our work. Skip anything I've already answered.

When you have enough, give me one thing: standing instructions under 200 words, written in the second person, that I can paste into Personal context.

Paste the result under Settings and help → Personal context → Add. It applies from the next chat onward. If the interview stalls because you can’t answer “what do we turn down”, that is a positioning gap, not a Gemini problem, and it will show up in every client draft until you fix it.

Step 2: Organize the client’s material in Drive

Right now, a client’s material is spread across their inbox, your inbox, a shared folder called “Assets,” and a file named final_v3_actual. Gemini can’t fix that. Three folders per client can.

• Brand — voice guide, visual identity, words they use and avoid, what they never say.
• Offer — current products or services, pricing, positioning, proof (case studies, testimonials with permission).
• Delivered — two or three pieces of work the client approved and liked, so the assistant knows what good looks like for this account.

Three, not ten. If your account manager can’t tell in two seconds which folder a file belongs in, the folders stop getting filled within a week and the system dies. Old pricing sheets and last year’s campaign go into an Archive folder outside these three, where nothing downstream can see them.

Step 3: Build a NotebookLM notebook per client

A Drive folder is everything you own about a client. A notebook is only the set you chose. That difference is why the notebook exists.

Skip the notebook if a client has three documents total. Attach the Drive folder straight to the Gem and move on. The notebook earns its place once a client has more than a handful of files, for three reasons:

• It is curated. Nothing from the archive leaks in.
• It cites. Every answer names the document it came from, so you can click through and check before anything reaches the client.
• It is one thing to attach instead of nine, which is why you will still be using it next month.

Create the notebook at notebooklm.google.com and add 5–10 sources from the three Drive folders: the brand guide, the current offer page, the questions their customers actually ask, and two pieces of approved work. Don’t add more. Ten pages of current, accurate material beats a hundred pages of mixed material every time, because the mixed hundred is exactly where the wrong answers come from.

Test the notebook before you build on it

Open a normal Gemini chat, attach the notebook with the + button in the prompt box, and run a real agency question with four extra rules.

Use only the sources in the attached notebook.

What are the three decisions [Client] needs to make before we start the [campaign or deliverable] work, and why?

Cite the source for every factual claim. If something isn't supported by the sources, say "Not found in the selected sources" instead of guessing. Flag anything that looks outdated, inconsistent, or missing.

Each rule does one job. “Only the sources” stops it from reaching for the web when the brand guide already has the answer. “Cite” turns it from something you trust into something you can verify. “Flag outdated or inconsistent” is more useful than it sounds, because client documents disagree with each other more than anyone expects. “Not found” matters most.

Step 4: Build the client Gem

Everything in Step 3 works, but every new chat means attaching the notebook again, re-framing the question, and reminding Gemini how the client sounds. A Gem is a saved version of Gemini that already has all of that. The notebook is what it knows; the Gem is how it behaves.

Behavior is three things, and most people only write down one: where it gets facts, how it writes, and how it decides. The last one is the one nobody thinks about. Every time you ask what to prioritize for a client, the model makes a judgment call. Without instructions, it makes that call based on what a generic agency would do. It should base it on how your agency decides for this account.

Go to Gems in the left menu, create a new Gem, and paste this into Instructions. Fill in the brackets.

You are the [Agency] account assistant for [Client].

[Client] sells [offer] to [audience]. Their voice is [three words]. Our role for them is [scope, e.g. monthly email, paid social, blog content].

Sources
Take facts about [Client] only from the notebook attached to this Gem. If a fact isn't there, say so and ask me rather than answering from general knowledge. Cite the source for every factual claim about [Client]. You may use the web for market or competitor research; label it as outside information and keep it separate from facts about [Client].

Writing
Match [Client]'s voice, not ours. For every draft, tell me what it's for and the one message it carries, then give the draft, then list any factual claims I need to verify and anything that needs [Client]'s sign-off. Never invent a price, testimonial, result, guarantee, or any legal, financial or medical claim. If a fact is missing, ask for it.

Deciding
When I ask what to prioritise, rank in this order: [rule 1, e.g. anything with a client deadline this week], then [rule 2, e.g. work tied to the live campaign], then [rule 3, e.g. everything else]. Push [what you deprioritise, e.g. redesign requests with no brief] down the list and say why. Always tell me what you moved down and the reason. Flag anything you can't rank because information is missing.

Variables to replace: [Agency], [Client], [offer], [audience], [three words], [scope], [rule 1], [rule 2], [rule 3], [what you deprioritise].

The sourcing block repeats the rules from Step 3 on purpose. In the chat, they applied once. In the Gem, they are permanent. The web rule in the middle deserves a second look: a flat “never search the internet” would be wrong, because you do want it checking the client’s market. The rule that works is that it may go outside; it has to say so, and it never sets outside material next to the client’s own facts as if they were the same thing.

Attach the notebook to the Gem, not to the chat

Under Knowledge in the Gem editor, add the client’s notebook and save. From now on the Gem carries the client’s knowledge into every chat, and anything you add to the notebook later reaches the Gem without you touching it again. Attaching a file in a single chat doesn’t do this; it lasts only for that chat.

Now open the Gem and ask the Step 3 question again with nothing attached. The answer should come back in the client’s voice, with citations, and with a line at the bottom saying what it pushed down the list and why. It is ranking with your logic instead of its own.

Step 5: Add the client’s look

The Gem writes like the client but has no idea what their work looks like, so every visual request starts from a blank description of colors and style. Gemini makes things three ways: image generation for assets you will reuse, video for a few seconds of motion, and Canvas for anything that is a document, a deck, or a page rather than a picture. You don’t need to master any of them. You need one more block in the Gem so it stops asking.

Add this to the Gem’s instructions underneath the three blocks above.

Look and feel
[Client]'s audience should see themselves in the work and feel [feeling]. Visual personality: [three words]. Colours we use: [list]. Colours we never use: [list]. Photography or illustration style: [description]. Formats we produce most: [e.g. Instagram carousel, email header, one-page PDF]. Never include logos we don't own, invented dashboards or screenshots, stock clichés, or text that won't be readable at size.

When a draft needs a visual or a document, don't wait to be asked. Make a first version with whichever of image, video or Canvas fits the job, say why you chose it, and leave clear space for headline text.

This goes in the Gem, not in personal context. Personal context is read before every chat you ever open, so it stays small and about you. A specific client’s assistant lives with that client’s Gem. Ask the Step 3 question a third time, and the first item on the list should come back with a draft already made, in the right format, with a sentence on why it picked that format over the other two.

Step 6: Set the line where it stops

At this point the Gem knows the client, writes like them, prioritizes like you, and produces drafts without being asked. That is also the point where it gets dangerous, because it now makes judgment calls on the client’s behalf and nobody has told it which ones aren’t its to make. Add this as the last block in the Gem.

Where you stop
On your own you may research, summarise, sort, categorise, draft, prepare versions, and set reminders for me.

Stop and ask me before any of these: sending anything to [Client] or their customers, publishing on any channel, quoting a fee or price, changing a customer or campaign record, committing budget, agreeing to a deadline, or making any legal, financial, medical or employment claim.

If a task crosses that line partway through, do the part you're allowed to do, stop at the line, and tell me you've stopped and why. When you give me a plan, mark every item that needs my approval before it can move.

The second list is the one people argue with. “That’s most of the useful stuff.” No. Everything in the first list still happens on its own, all day. It researches, sorts, drafts, and gets things ready. What changes is that the last inch — the part you can’t undo and the client would notice — stays with you. That is exactly what lets you hand the Gem to a junior account manager and walk away.

Knowledge lives in the notebook. Behaviour lives in the Gem. You live in personal context. Change one without touching the others.

Day-to-day prompts

With the Gem built, you stop explaining and start asking. Every answer arrives in the client’s voice, with sources, a list of claims to verify, and a list of things that need sign-off. Three prompts cover most of an account manager’s week.

Draft a deliverable

Draft [Client]'s [deliverable, e.g. October newsletter] around [the one thing it should achieve, e.g. the early-bird offer]. Use the current offer and the approved pieces in the notebook as the reference for tone and length.

Check ideas against the brand

Here are [number] campaign ideas for [Client]: [paste ideas]. For each one, say whether it fits their brand guide and current offer, cite the passage that supports or contradicts it, and tell me which one you'd take to the client first and why.

Prepare for a client call

I'm meeting [Client] on [day] about [topic]. From the notebook, list what we've already agreed on this, what's still open, and any claim in our recent work they might ask us to back up. Mark anything that needs their decision.

The next client is a copy: same three Drive folders, a new notebook, a new Gem with the same instruction blocks and different brackets. Share the Gem with the team so one person builds it and everyone uses it.

Maintenance

The system decays in one specific way: the client changes an offer, nobody updates the notebook, and the Gem keeps citing the old pricing with full confidence and a source link. Three habits prevent it.

• When a client sends a new brand guide, offer sheet or approved piece, it goes into the Drive folder and replaces the old source in the notebook the same day. Replace, don’t add. Two versions of the price list in one notebook is how contradictions start.
• Once a quarter, open each client notebook and remove anything no longer current. Re-run the “not found” test afterward.
• Every few months, reread your personal context. Roles change, agencies reposition, and standing instructions written in January are quietly wrong by June.

Frequently asked questions

What to do next

Pick the client whose brand guide you know best. Build the three folders, the notebook, and the Gem for that one account, and run the “not found” test before you trust any of it. The second client takes a third of the time.