Cheating
Use /report <player> <reason> in game. Do not accuse the player in public chat; that starts arguments and can interfere with an investigation. Repeated public callouts after being redirected are treated as harassment. If you have a clip or screenshots, send them privately through the Discord. An anticheat runs on the server and staff read what it flags, so evidence speeds a case up rather than being the only thing that counts.
Dupes and exploits
Use /report-server <reason>, report it privately, and do not use it. Report it and you keep your account. Quietly farm it and you will not, because prices here are set by players and a dupe ruins that for everybody.
Bugs that are not exploits
Anything broken but not abusable can go straight into the Discord. Say what you did and what happened instead.