Adding cams to Ring Doorbell 2

I am going to get two more cameras, wireless outdoor Ring Spotlight Cam. Do I need to buy anything else, like some kind of hub to connect it all? I'm new to this. I understand I will have to upgrade to the more expensive Ring plan to have more than one device. Just wondering if there's anything else to consider since this is getting pretty pricey. Came in handy though, my No Stalking Order I have on someone saved me. Woke up at 6:30 am, still dark out, pulled up my Ring Doorbell 2 before I even turned any lights on... he was sitting in my driveway. And walked up and tried my door handle. Got it all on video. Along with all the police interaction. A little disappointed that I can't make out most of the talking from only 10-15 feet away though. But it got what I needed. Now I just need to protect the back of my house.