"To grow a fanbase" means to attract and gather a group of people who strongly support and admire a particular individual, group, or brand. Full definition
Ask them to help spread word about your page and then grow your fanbase that way. (madgeniusclub.com)
Despite his decision to take a creative back seat to the game, he does admit to being excited to follow the games development at the hands of the games growing fanbase. (northlandsquare.com)
Miketendo64: Lastly, is there anything you would like to say to your ever - growing fanbase of readers and supporters? (miketendo64.com)