Level 50-54 in Maplestory: At this point, Jr Yeti should be fair game, and you will make quite a profit. Drake's Meal Table is also a fine choice, although you probably will not net a lot of profits. Another alternative is Luster Pixies: although the drops are not stellar, you will find a lot of Dark Crystal ores and Gold ores there. On another point, Copper Drakes at Dangerous Valley now becomes a lucrative choice.
Also, a wise choice would be to start Ludi Maze PQ right now, if you plan to do this be prepared to take down Tauromacis. Zombie Lupins are also a good training spots as they spawn fast and drop a decent amount of mesos(Maple Story Meso).
Level(Maplestory powerleveling) 55-60: Zombies are the second best leveling spot. Go slaughter them left to right, then back to left again. Alternatives include Drake's Meal Table, Cargo's Area, and the Crown Flyer. If you have not started Ludi Maze PQ, you should attempt it now. Averaging in about 10,000exp each run, each run should take you about 1-2min. Ludi Maze PQ is the best leveling spot.
Level 60+: Forest Of Golem is a very good choice for the funded. The spawn is excellent, and everything is close, making for fast leveling. By this level with a decent weapon you should be able to 2-HKO the dark golems and 2-3HKO the Mixed golems with Savage Blow. Along with that they drop Gold and Black ores, 60% Glove Attack scroll, tobis, and Dark Crystal ores. Zombies can also be a strong alternative, however they are spaced out unlike FoG which can be troublesome for bandits. Ludi Maze PQ is an excellent choice, even if some players can attack you due to a rare glitch.