What are the best classes for a halfkin? Are halfkin's good healers or magic DPS? Pros and cons? Sorry for all the questions, i'm just very confused.

Halfkins are great Healers and Magic DPS and they also have good Racial Skills. But the Cleric passive on halfkin isn't actually good when it comes to healing, since it increases M-CRIT DMG, good for battle Clerics. The passives for Warrior and Thief for Halfkin is also good, but they are kinda squishy, unlike humans.

Actually, the passive on halfkin cleric increases mcrit rate, which is great for both healing and dps clerics. Heals can crit, and some healers build themselves around mcrit rate, so the more you can stack the better.