Open AI usage limitations

Hi, I need your help.
I am playing with Bubble and OpenAI and I am just scratching the surface for now.

My intention is to build an AI-Writer, available for free. What is the best approach if not using accounts/users to limit usage? Should I consider adding users to the app? If I keep this free (public) what about bots or not fair use, when users will use too much? Any advice for these situations?

Thank you!