You are welcome to purchase tickets for friends – there is a 1 device limit per ticket, so multiple people cannot watch the same stream unless they are together.
When an artist creates their LiveStream, they will get a unique ticket url that they can share with fans who want to purchase.
You can definitely share that with your friends as well to help the artist promote their LiveStream. The more watching, the better for the artist and the more exposure and money they make!
Just make sure to reach out to the artist that you are buying a ticket to see and they can send over their URL so that you can buy a ticket from them.