First aid kit for fish - Is this something people do and if so are there recommended supplies to put in the kit? Suppose there's meds that are good to have on hand?

In terms of medicines? I probably wouldn't keep any on hand because they have expiration dates. I would just search for where I can find the most common meds I might need in an emergency. For instance, see if your local pet stores / fish stores stock them. That way if you're in a hurry and need to quickly get your hands on some you won't need to go around to multiple stores trying to find them.