I killed level 29 Orc Sergeants for 5500 sp. I used platinum super skill pill, sp booster, and the training spell book 50% Tera Gold sp, to get a max of 72,000 sp a kill. Never could figure out the math, as I always got a higher sp number.
But I found to use the other spell book of 15% to get like 61k sp a kill that is if you are buying the training spell books.
Now this method works, ONLY if the person being power leveled is strong enough to give the coup de grat or killing blow to the monster. Having a high upgraded weapon helps a lot if you are using this method.
If not, then the monster can be slightly downgraded. This works good too if a rogue or a knight is around. They can snare or stun before going back to town.
METHOD 2 - You can also be in a 2 man combat party, but the person leveling must have recall. A combat party you get xp for the monster you kill now.
So you both hit monster till it is nearly dead. Then the other person takes a recall to lose aggro. Then the other person kills the mob and gets all the xp.