Well are you looking for a subscription or pay-as-you-go API usage?
Subscription? -> Google One plan (http://one.google.com/)
API? -> AI Studio (https://aistudio.google.com/)
It's not really any different than the choice you'd make with OpenAI/Anthropic depending on how you plan to use it. Except as a hyperscalar, it's also offered first party from Google Cloud (like Claude via Amazon Bedrock or GPT via Microsoft Azure OpenAI Service):
Google Cloud -> Gemini Enterprise AI Platform (https://cloud.google.com/ai)
But if you're using models via OpenCode or Pi or whatever, the flow chart is basically just "Go To AI Studio" unless you or your employer is already used to Google Cloud, otherwise there's no need to subject yourself to all those enterprise-y IAM dashboards and stuff. You still get free usage from AI Studio when you generate the API key without needing to add billing details so very easy to try.