I’ve set GIPHY up on one of my sites and I haven’t used the “Upgrade to Production” button. I do recall having a false start setting it up, but I don’t recall the details at the moment.
The API key is easy enough to find on the GIPHY dashboard. Make sure it matches giphy api key in the discourse-gifs theme component settings, I guess? The only other non-defaults I have set are:
giphy content rating= “pg”limit infinite search results= true
Of course I also made sure the component is enabled on the default theme.
Not sure this helps you, though. :-/