The Level-6 Orange Mushroom, aka Easy cheesy!

By level-3 in the tutorial you have, or SHOULD HAVE the knack of how to fight and avoid all of the little stuff, like the tiny Shrooms, the blue and red snails, and not hurt yourself too much in the process, however around Lv5 of your training, you'd be asked by Mai of Maple Island to hunt down 5 Orange Mushrooms as part of your training, and the oranges are considerably tougher to kill than anything before it, but if you've learned how to jump up to attack a monster on a platform slightly above you with good timing, you could damage and kill said monster and not take any damage in return.

Just hunting those five orange mushes is enough to take you to 70% through Lv5 to Lv6 in short order... hence why I loved to hunt these things, as anyone at Lv6 or higher should have no trouble mass grinding on these things to quickly level up if you decide not to run any quests. In fact there is "An empty house" on a "Hidden street" where you could find an entire small map FILLED with these things, and grind EXP like you wouldn't believe was possible, even for someone at Lv20!

Sure my previously posted Green Mushes give you more EXP per kill, but considering a Green Mush has roughly 3X the HP of an Orange mush, and has higher defense stats which are hidden, you're much better off going HAM on these oranges than on the greens. Plus the fact that Bruce the scientist in Henesys town offers a quest which you hunt a few oranges for their caps, and a few "tiny" shrooms for their spores, you get easy additional EXP to level with, and a nice reward of a handfull of red HP and blue MP potions.

Side note as far as genuine classic Maple is concerned: The leveling multiplier was a one to one ratio, while Artale and perhaps even Nexon's own Classic World may have 2x or even 3x EXP booster to help everyone out of the starter stage of game play... but if you ask me, monetarily speaking, it's rough for a true first time player to edge by at such a rapid leveling pace, even if grinding mainly on these oranges, because while the starter potion packs are a nice booster indeed, grinding at a glacial pace early on does have the benefit of GETTING FUNDED rather well and again, these Oranges are a good source of Meso since they are easy cheesy to MURDER! xD

Anyhow Maple by Wiz and Nex of S. Korea
Fanart and convenient reference sheet by  nezumiyuki