Update README.md (google-gemini#2729)

Co-authored-by: Allen Hutchison <[email protected]>

Author: 2 people

README.md

@@ -38,9 +38,9 @@ With the Gemini CLI you can:
 
 You are now ready to use the Gemini CLI!
 
-### For advanced use or increased limits:
+### Use a Gemini API key:
 
-If you need to use a specific model or require a higher request capacity, you can use an API key:
+The Gemini API provides a free tier with [100 requets per day](https://ai.google.dev/gemini-api/docs/rate-limits#free-tier) using Gemini 2.5 Pro, control over which model you use, and access to higher rate limits (with a paid plan):
 
 1. Generate a key from [Google AI Studio](https://aistudio.google.com/apikey).
 2. Set it as an environment variable in your terminal. Replace `YOUR_API_KEY` with your generated key.
@@ -49,6 +49,8 @@ If you need to use a specific model or require a higher request capacity, you ca
    export GEMINI_API_KEY="YOUR_API_KEY"
    ```
 
+3. (Optionally) Upgrade your Gemini API project to a paid plan on the API key page (will automatically unlock [Tier 1 rate limits](https://ai.google.dev/gemini-api/docs/rate-limits#tier-1))
+
 For other authentication methods, including Google Workspace accounts, see the [authentication](./docs/cli/authentication.md) guide.
 
 ## Examples