There are several problems with the server itself.
-The spawn looks very unappealing.
-The claim zone is tiny, meaning you can screw up the spawn area by just walking out within easy viewing distance and making a bunch of ugly junk.
-Speaking of ugly junk, it looks like the spawn's immediate outside was raided, and no, I don't think calling it design would help.
-/pl is usable, revealing TrollGUI, which won't impress the mature members that come along.
-You use AntiCheat+, the undoubtedly crappiest anticheat plugin you can download with the greatest amount of false alarms I've seen since the original AntiCheat. NoCheatPlus, by contrast, is reasonable. with AC+ I can modify the game timer just by walking >.<
-It's pretty easy to make out the sphere brush dirt blobs that compose of the spawn. A little smoothing would help.
-Listing warps permission is denied. I guess if that's what you want?... but there's still ways to block people from seeing/accessing warps without not including an otherwise common permission.
-In combination with the above starting problems, your factions server has nothing to distinguish it as being superior to another factions server. It is the same thing as people would get on other servers; yet the other servers are, being quite honest, more likely to have a better introduction.

I don't think you have an advertising problem so much as a content problem. Fix the server and make it look decent for new joiners, and then you'll probably see a few more people sticking around. In other words, finish the server, then look for players.

Servers don't always get popular straight away. However the key to it is making it unique and different to others, features some people may not find elsewhere. There are also multiple sites you can advertise your server on, like PMC itself.