Basically, to grow Ramble, existing users could invite specific people instead of advertising broadly. Quality > quantity
Since registration needs to be turned off right now anyways because of abuse, to grow the user base current users of the site could invite specific quality people from other sites, maybe with invite codes or by just sharing a secret date that registration opens. Those invited people can invite others and at some point we might have enough people that registration can be open to everyone again because there will be more people coming on the site regularly and moderating or reporting illegal activity. Invites aren’t great for the privacy of either the inviter or invitee but could be used in the beginning to get a really good user base that will attract more quality users after the forum is opened up.
For a free speech site to really change society, it needs to have an influence on the thinking of at least some people who have high positions in society, such as CEOs, business leaders, as well as high earners who can fund solutions, people with the technical skills to implement solutions, academics who can influence the culture in universities etc. These tend to be smarter than average people who are turned off of a lot of the content on, for example, Bitchute or the .win forums. They usually don't have time or interest in sifting though nonsense to find the good content. I’m not saying to turn this into some kind of Mensa circlejerk, but it’s good for smart people to have uncensored forums to get info and ideas in front of other smart people for critique and discussion, without the space being flooded by theories about Q, black eyed children, demonic alien parasites etc.
r/conspiracy on Reddit has a lot of good content and is one of the only major spaces left for relatively free speech on Reddit, but there are a lot of gullible people there too. Occasionally I see users on r/conspiracy who stand out as critical thinkers who are not just parroting the latest thing from Stew Peters or Charlie Ward. Sometimes they only have a few upvotes because most people have attention spans too short to read through what they have to say. So those are the kinds of people I would want to invite. I sometimes save interesting Reddit posts I come across so I could go through them and invite some people. Other people might want to invite good posters from other forums they go to. It could be people from Linux forums, programming forums, investing forums, or whatever. I think the main thing is to not invite too many users from other small free speech platforms, so that other free speech platforms are not made worse by siphoning away the best users.
Aside from schizo theories like “Sodomy taught by Dracos to Nazis as Atlantis art to infuse LGBTPB demon spirits to create child sex slave alters” (that's a real Bitchute video description), another issue on certain free speech sites, though some consider this a feature, is that some sites (like voat) are echo chambers that drive the vast majority of people away. To be clear, I don't think people should self censor and still think all speech should be allowed here, but as long as we're inviting a variety of people from different sites, it won't become an echo chamber and “I wish the holocaust actually happened” type posts will not be frequent enough to drive potential users away. The main practical precaution, if inviting leftists, would be to avoid inviting people who are pro-censorship since they might try to ruin the website any way they can.