Maybe things have changed but it was a big mess trying to getting an API key from Google as an individual a few years ago. Way too much conflicting documentation.

Eventually I gave up and run a few hundred million tokens (edit a few billion) through openrouter.ai using Gemini Flash 1.5 to Flash 2.5

Every since price increases on Flash 3.0 I've stopped using Gemini, too expensive for basic classification, sentiment detection, ocr etc.

As other posters said Google assumes you are some bigcorp trying to use their products. The Vertex versus AI studio confusion did not help.