I've seen so many people say the jest of it when they mean the gist of it that I'm afraid it will be one of those things that comes into common use, not because it makes any sense, but because everybody's doing it.
If someone says something and you get the essence of it, you get the gist of it. A jest is a joke. You can only get the jest (of it) if someone was being funny.
If someone says something and you get the essence of it, you get the gist of it. A jest is a joke. You can only get the jest (of it) if someone was being funny.