I love OpenRouter, since it is a simple way to get started and provides a wide range of available models.

You can buy credits and set usage limits for safe testing per API key to gain access from many AI models through one simple and unified API from all popular model providers (OpenAI, Anthropic, Google, xAI, DeepSeek, Z.AI, Qwen, ...)

Ten dollars is plenty to get started... experiments like in the post will cost you cents, not dollars.

Gemini has a generous free tier (2500 prompts per day), all you need is a Google account to get an API key.

Most cloud providers, like Azure have free credits at the start. On azure you can deploy your own model and pay with the free credits.

You can just stick a tenner in OpenAI though and it won't charge anymore than the credit you've put in

and sorry, forgot you can also run local models aswell :)