You can't say something is "gay". Not only does that not make any sense, but it's also so incredibly rude and ignorant. When you say that something is "gay", you make yourself look uneducated and immature. When someone uses "gay" to describe something, I automatically discount whatever they are saying. My brain says, "Note to self, this person doesn't seem to be able to say intelligent things. Stop taking them seriously, ever."
Also, as a mother, I really need you to not say this around my children. I am raising them to know that being gay isn't something to make fun of. I am trying to build tolerant, kind children who see all people as equals. And I can't do that when you try and use "gay" as an adjective.
There are a myriad of other perfectly wonderful, sensible words to use instead of "gay". Take the time to look them up and you are already well on your way to becoming a mature adult.