Generate Instagram posts from Google Sheets with Gemini

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Social media agencies waste hours manually turning content briefs into finished Instagram posts. This AI automation bridges the gap between a simple spreadsheet content plan and a fully published post, handling concept generation, image creation, and caption writing without anyone touching the process.

What This Automation Does

Reads unprocessed content ideas from Google Sheets on a schedule, picking up topic, audience, voice, and platform fields entered by the client
Uses Google Gemini to generate a platform-specific single-image content concept and two distinct AI image prompt options from each idea
Passes the selected image prompt to a Replicate image model to produce the final visual, then writes a tailored caption to accompany it
Publishes the completed image and caption directly to Instagram via the Facebook Graph API and marks the row as processed in Google Sheets

Tools Used

n8n
Google Sheets
Google Gemini
Facebook Graph

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How To Build It

Wire Google Sheets as the content source

Configure the workflow to poll a specific Google Sheets tab on a timed schedule, retrieving only rows that have not yet been processed, so the same idea is never published twice.

Build the Gemini concept generation prompt

Map the Topic, Audience, Voice, and Platform columns from each row into a structured prompt that instructs Google Gemini to return a single-image content concept plus two distinct image prompt options as a parsed JSON output.

Generate the final image via Replicate

Send the chosen image prompt to the Replicate Flux model through an HTTP request, poll for completion, and retrieve the finished image URL ready for upload.

Write and structure the Instagram caption

Pass the approved content concept back into Google Gemini with a caption-specific prompt that applies the client's defined voice and platform conventions, returning a publish-ready caption with hashtags included.

Publish to Instagram and log the result

Upload the image and caption to Instagram using the Facebook Graph API two-step container-and-publish flow, then write the post ID and published timestamp back into the originating Google Sheets row to confirm completion.

Pitfalls

Instagram's Graph API requires a Business or Creator account linked to a Facebook Page, and the access token expires every 60 days by default. Clients who rotate passwords or disconnect the Facebook Page will silently break publishing until the token is refreshed.
Google Gemini can drift in output format across requests, returning malformed JSON that crashes the structured parser mid-run. Build in explicit output validation and a fallback retry so a single bad generation does not stall the entire sheet queue.
Replicate image generation is asynchronous and can take anywhere from 10 to 90 seconds depending on queue load. Without a proper polling or wait loop, the workflow will attempt to publish before the image URL is ready, resulting in failed posts that still get marked as processed.

FAQ

Can I build this without coding?

Yes. The entire workflow is configured through visual tools in n8n, and the most technical steps are setting up API credentials for Google Gemini, Replicate, and the Facebook Graph API. If you can follow API documentation and fill in credential fields, you can build this.

How long does it take?

Expect 6 to 10 hours for an initial build that covers credential setup, prompt engineering, the image generation loop, and end-to-end testing with a live Instagram account. Add another 2 to 3 hours if the client needs a custom Google Sheets template and a handover walkthrough.

What can I charge?

Pricing is yours to set based on your positioning and the client's scale. Productising it as a fixed-scope done-for-you setup with optional monthly maintenance tends to command more than hourly billing, since the value is measured in staff hours saved per week rather than your hours spent building.

Which tool is required vs optional?

Google Sheets, Google Gemini, and the Facebook Graph API are all required since they handle the core data input, content generation, and publishing steps respectively. Replicate is the image model used in this workflow, but it can be swapped for another image generation API if the client has an existing subscription elsewhere.

This is original DigiNo analysis. The underlying automation pattern is a community workflow template – view the original on n8n.