Whatever level you are now, you are definitely 33+. This means you can now do Robo. Pick up the quest from Shutian, and spam the crud outta the quest. Try hard to Win it, because the exp from it to a lv 33~39 is much more then 40-46. Between KQs, do your quests. Remember to ask your Academy for help if you have problems! Especially on Boss quests. You should easily hit 40.

Levels 40-50

These are rougher, and harder. There are a lot of repeat quests though. Make sure every single level, you check your quests to find repeats. If you didnt get fiesta gold KQ Robo, keep doing it until you get him. Some of the repeats youll get are..
At 41 and 42 you have Ugly Goblins 2, which is killing goblins
At 43 you have A bet with Marty 2, which is killing Goblin Swordsmen
At 44 you have Fantastic Items, which is collecting Werebear Claws
At 44, 45, and 46, you have The Broom Stick of the Best Qualities 3, which is collecting Armpit Hair from Werebears
At 46 you have The Best Medicine for Athlete's Foot 3, which is collecting Shroom Heads from Sand Mushrooms (the monster, not the herb)
At 47 you have A Secretive Request, which is collecting Goblin Captain Helmets
At 49 You have Lips Of Mannequin, which is collecting Lips from Mini Lips

Again: a party really helps, and if you can find a higher level archer or mage to help you, it goes loads faster. Dont be afraid to use all those Elderine scrolls you got from 20-40. Now is when youll use them, it makes this go a lot faster.

If you get stuck on a level, try Honeying KQ. For levels 40-45 youll get fiesta gold about 10% for trying to do it, even if you fail. The KQ quests give huge exp. Also, try the Epic GC quests, or the Dungeon quest to get out of a stuck level. Once you hit 46, do the Mini Dragon KQ as much as possible, and do the quest for it too.

49 tends to be the really hard level. All you really have is lips, which gives less exp than werebear hairs, shroom heads, and gob captains. But its all you have. If you were good about spamming the repeats, then youll have loads of other quests in your arsenal. Do these to lvl.

If you still cant lvl to 50, try doing MD more, or check out the abyss. I advise you do MD more though, as the PKers in abyss can ruin all your grinding and MD from 46-50 gives excellent exp.