Okay, so this comes from me, a guy who has owned soooooooooooooooo many Garry's Mod servers. The goal is to get as many friends (doesn't have to be many at all) and have them all on the server at once to make your player count go higher up. There will always be people looking for smaller and newer servers, whether it is to get a high rank early on, just be a part of something new, or escaping some other server. When you get new players, there needs to be a combination of good content and making them feel valued (And I don't mean just make them feel valued, like actually value them), and they'll hopefully come back. It is kind of a snowball effect, the more people you have on your server at the same time, the more likely someone else is gonna notice and join.