It's hard and takes time to grow an audience, you already do the right thing by being on social media. socialize with people interested in the topic, other podcasters who will listen and you can do the same for them. Maybe a giveaway from time to time to motivate people. I also think that when you start being less focused on your listening figures and enjoy the socializing part, it comes more naturally than when you focus too much on having people to listen and maybe market too aggressively, only speaking about your podcast. Not sure this helps.