The way I engage with people who complain all the time to an annoying level is at first I just completely stop engaging when they start up again. Don't reply to anything, no "uh-huh's" or "wow, that's crazy" or other obvious signs that you're not interested in anything they're saying. Instead now I just hijack the conversation and always try to steer it to something else. If they're the type of person who will eventually bitch and moan about any topic you try and change the convo to, they I just start straight up calling them out: "Hey you're complaining again" or "you're doing that thing with your mouth that sounds a lot like whining". If after all that, they still don't make a conscious effort to change their behavior, then just cut them off completely. Not worth the time and effort, especially if you've only known them for a few months. You might not realize this until your 30's, but the sooner you cut people out of your life that only cause/want to talk about drama all the time, the happier you will be. You have enough shit to worry about already with your school, your family, and your job, etc....