Same experience. I think at the beginning you need the opposite, i.e. either you/your team/your friends to kick off a lot of content or it'll hardly take off.
It also depends on your site. For example if you display content in chronological order like Twitter, then you incentivize people to spam as their content is immediately visible. I.e. my first post will likely be "test" - if I see it in the homepage then I delete it and post a link to any of my projects (if not worse).
Finally, moderation shouldn't be massively complex at the beginning. Just implement a super downvote (that maybe only you/your friends can see) that kills content you don't want to see with 1 click.
Good luck, looking forward to a show hn!
