The community generally recommends purchasing official items with real money and selling them in-game to avoid bans.
If you are using a site like PlayerAuctions or G2G (which carry significant risk), sellers often require specific details in the "Note to Seller" field: Server: [Server Name, e.g., Erinn] Character Name: [Your In-Game Name] Delivery Method: [Mail/Auction House/Trade] buy mabi gold
Wait for official sales to get high-value items that sell for millions on the player market. Third-Party Marketplace Notes buy mabi gold