Attracting and keeping players online is a long process which includes properly advertisments, server management and a stable build of the platform.
Server advertisment/server boost is the most popular way to promote your game server, with all of his features like:
maps, plugins, gameplay style, uptime, community events, anticheat system etc.
You can use any social media for advertisments just by creating content like:
screenshots, videoclips and events so you can have the players attention and engage them with your posts.
Now days there is a many free or prepaid websites for server boost,
you just need to check those websites statistics and activity, and carefully choose the one you think might be in your service.
The server managment could affet the player base in many ways. Server owners are aways responsible if something happens in their servers.
If you want to avoid any problems with the platforms you need to check often for updates and check if there's any records in the server logs, so you know if anything is broken.
Another important thing in the server management is how the administrators rule the server in your absence.
You need to create server rules for all and make them visible in the server, so you can be sure everbody sees them.
If you want to create a stable build of your platform you need to check in the search engines which modules are compatible with the others,
because there is a many small details, which may cause a big problems even crashes.
The best way to create a stable platform is to use the latest modules from approved creators and websites.
The plugins you're using in your server must be aways local compiled and the source code must be aways aviable in the scripting folder, so you can edit them if needed.
Another important thing is the fast download known as "sv_downloadurl" which is used to set URL for clients to download custom content, such as maps, models, sounds and other files.
You need a web server or web hosting free space where you can upload and host those files.
This can be a dedicated server, a web hosting provider, or any other platform that allows you to serve files via HTTP.
Connect to your server and check if custom content is being downloaded from the specified URL or ask other players if they are able to download custom content successfully.