How do i go about getting people on a gmod server?

Remember that nobody wants to join an empty server - you might get the one or two odd players but they won't stick if there isn't a playerbase, funnily enough. You'll need to have concurrent players, and the best way to do so is to get your friends to join and play on your server. This goes for any gamemode as an empty server = a dead server! If you have a bunch of friends on, people will see that the server has players on it and will join, and from there you can establish a proper playerbase.

Hope this helps