@nydel I usually just make sure to guide them (usually in physical space) to some interesting stuff to subscribe to, depending on their interest. Some areas aren't covered yet which makes some peoples' interests harder to fulfill, but can also be encouraged to "be the first" to contribute cerrain aspects of the network.
Community building is the best effort to provide !GNUsocial as a usable and meaningful means of communication. To rediscover that awesome "whoa, random people who are NICE"-feeling that was so abundant on the internet just 10-15 years ago.