Welcome. Usually just posting the link on other social media to get people to join. My server can handle a good bit of users however, I have no financial backing so, everything here is on my dime 😁. If the site ever grew to the point where I needed to upgrade, I'd would consider that when the time came.
Just something to keep in mind. Achieving network effects (or reasonably fast growth) is somewhat of a Catch -22. Attracting more users requires both more content (anything deemed to be worthwhile whether posts, topical conversations, better known people who use the site to get their message out, etc) and more users. And the growth in both of those is significantly driven by number of users.
BTW, the look and feel of your site is very nice and clean. Keep up the good work!