The required bandwidth depends on the number of notifications you are planning to push every day. Each notification is relatively small (for Apple Push Notifications - up to 256 bytes payload + some overhead < 400 bytes per message; for Google Cloud Messaging - up to 4K bytes payload + some overhead < 5K bytes per message). You can do the math.
In addition, for Apple Push Notifications your server must allow connection to outgoing ports 2195 & 2196. I'm not familiar with Nodejitsu, so I can't give you more specific information.