While this is more meta talk for admins and mods and there are other subs for this type of stuff I’ll take a stab at it.
basically from a social media perspective you need to be creative content. For that you need to examine the types of content your audience engages with and play to that. That is relatively easy with an active subreddit that already categorizes your audience. In terms of internet culture though the majority of subreddits are probably memes and sharing links. Leaving the idea of content creation to other sites to host and lead the way.
People have adapted this by actually pairing websites or creative pursuits to a specific subreddit also moderated by the creator or aimed at discussing the subject matter.
There are some answers and conflicts of interests that have arisen with such moderation. What happens when a moderator starts using their sub for personal gain when the goal of the sub is really general? Its a tough moral hazard that might stifle the true discussion. They key is really to be the king of content. If you keep producing relevant content then you will be a trusted source.
Really subreddit growth is mostly the same as facebook page growth and engagement but it allows for a greater democratization of authority and discussion depending on how you structure posts.