Are you suppose to script custom emotes and dances?

Yes, they are created in a script. You need to register a key to an emote, for example, "wave". Now, for this to work, we need an animation, so, say we have an animation which makes your character wave. For us to bind that animation to a key, we would script something like this:

function onKeyPress(actionName, userInputState, inputObject)
    if userInputState == Enum.UserInputState.Begin then
        game.Workspace.wave:Play()
    end
end

game.ContextActionService:BindAction("keyPress", onKeyPress, false, Enum.KeyCode.R)

You can build on that.

Your question is just a request, so I'll briefly explain the steps: I believe roblox already has a few. But yes, you can make them.

Step 1: Make an animation. You can check how to make an animation on the wiki. Step 2: Have a remote event, and a script waiting to be fired. Once fired, it binds the animation to the player, pretty much. Step 3: Have a local script in the player, in which can fire off the event. You can go about this in 2 ways: - Have it go off when a certain key if pressed- OR - Have it go off when a certain thing is chatted-