As marketing trends changing how you get your message out there on a daily basis, it is often difficult to build an audience on social meida. The only constant is the increasing reachability of your audience.
However, getting your message to your current followers is preaching to the converted. Reaching beyond them to their followers takes a little work. For example, engaging those people in conversation, and above all, being usefully informative is more likely to draw them in than an aggressive call to action.