Gifting pearls is 90% of the time, a scam.
Anyone who asks for pearls just to Post something, is scamming you.
A "legitimate" use of the gifting system (this borders on RMT so i dunno if kakao views it as legitimate), is a "thank you gift" after winning a rare item. The buyer and seller will make arrangements to ensure (or at least drastically increase the likelihood) of the buyer winning the item, and then the buyer will gift the seller with either pearls or a pet or costume or whatever was arranged before hand.
For example, the buyer will say "I have a pre-order up in Valencia for a +9 Dandelion Great Sword, post a +9 Dandelion Great Sword in the Valencia market. If I win i'll gift you a Cat Pet." Or the buyer/seller may make arrangements to post a T8 Horse at a precise time when not as many players are on. They will generally get in the same voice chat so they can coordinate the exact moment the seller posts it so that the buyer can grab it right away.
of course, the buyer can also scam the seller this way, there is no mechanism to enforce that he actually gift afterwards. It takes some trust obviously but either way, the seller at least gets fair market price for the item he was selling. For big ticket items like T8 Horses or dandy's ppl like to confirm it via voice chat. less likely the person will scam you if they are willing to talk to you in voice.
I'm working on getting a pure black T8 (leveling up all my T7s with the right skills and colors, wish me luck) to hopefully awaken into a Nightmare when they add the T9s to the game. Once I have it it's not something that I'd want to sell, especially not for the piddly 200-240mil that the stable says it's worth. But if someone came along and offered $100 bucks worth of pearls, on top of the in game cash? I mean, shit. can always breed more. But yeah i'd definitely need the motherfuckers home address and shit and talk to him on discord before I agreed to the trade