Most features on Discord are free. It doesn’t cost anything to join and create servers. But there are some services that cost money.
You can pay to upgrade your account with Discord Nitro or Nitro Classic, which costs a little less and provides fewer features than the full version.
Nitro upgrades are linked to your account, not your server. And most of their features benefit your account rather than your profile. However, Nitro does give you access to perks that help you run your server, like better resolution when you livestream and more backgrounds in video calls.
To unlock all the features for your server, you need to spend Server Boosts on it. Higher boost levels give your server benefits like higher audio quality and more customization options.
You get two free Boosts with a Nitro subscription. But to unlock the highest tiers, you’ll need to buy more Boosts or get other users to spend them on your server.