For all you low level magicians, watch out, 80+ damage. The place that people call the Slime Tree the Tree Dungeon South of Ellinia 1 and Henesys hunting ground. However, as you are still pretty low leveled, it could be wiser to stay close to Ellinia until at least level 10. Henesys Party Quest is a good option. After you reach level 20 or so, Perion which is ironically the maplestory mesos Warrior's town is a relatively good place to train, since the monsters, which are mostly stumps and their variants, have low magical defense and slow, good for magicians. The Kerning Party Quest is additionally a popular way to level, although it is recommended to be around level 24+ to have a higher chance of being selected for this PQ. Slimes and stumps at the map south of Ellinia will work wonders with your exp. Slime Tree is a great option because of the spawn rate of the monsters. You should have Energy Bolt handy in case a mob comes by. Never go to the tops of some of the maps or use the portals there, as higher level monsters will quickly kill you. You may want to consider going to Amoria, as the first map with monsters on it has orange mushrooms. Alternatives include the Henesys Hunting Ground, the maplestory meso Thicket Around the Beach II where you can safely attack enemies with Energy Bolt.