Just go on Voting sites like MCMP, PlanetMC, Minecraft Server List, etc etc. Alone I got a good 20 players to join off those alone in the past 5 days.
If you have money go on MC-Market and hire an advertising manager, get a trailer and get your players to re-upload that for rewards (Like crate keys)
Get YouTubers on your server. I'm not saying go hire Skeppy, or Technoblade. Im saying get smaller YouTubers (Around 200 - 2k subs) to join your server, and give them perks for recording on it. For example I'm giving YouTubers their own Star Code (Kinda like Fortnites Support a creator code) which they keep 10% of each purchase that people make with their code, and payment at the end of each season for recording on our server.
There are many ways to market your server that are free, or cost less than google ads, Facebook, Twitter etc, but if you do want to also use a social media platform to advertise on. Target users on Instagram. Find a Minecraft related page, and see how much it would be for an advertisement from them. Hope this helped! :D
