Had the same problem, wanted to use gemini but wanted to setup a speeding limit, turns out Google would prefer you to risk bankruptcy for a mistake, no spending limit available from what I understood, ended up going with openrouter and using gemini through them instead
Holy Crap, I got about 45 minutes into setting up billing and just gave up and un-did everything.
Hint: If you want to put a spending Limit on your google cloud account, its not trivial.
I will say that Stability AI is similar to Claude, they will just let you buy credits and hit an API.