Instakill question

I started using a hybrid build, and from what I understand I'm supposed to idle until I don't instakill monsters, right? If I'm not mistaken, "instakill" is when you don't ever see numbers on regular monsters, so the "dead!" just stays there besides bosses. So I guess the question should be, do I just put my 2 auto clickers on monsters or wait or what exactly? Do I get more gold when idling?