Level 1-5: You should work on easy level 1-2 Aibatts, and then work your way up to captains and then burudengs. By the time your done killing Aibatts, press I to go to your inventory, and click-and-drag your food to the F1, F2, F2, and so on buttons. Once completed, all you have to do during battle is press a key and the item activates.

Level 5-10: You should attack Demain Urchains, or pukepukes. By now you should know how to do basic functions such as heal attack, move, speak, and use new items.
Level 10-15 were the hardest levels in vagrant class for me to get through many think alike too. What you should begin leveling on is Lawolfs, Grownup Lawolfs, and Feferns. These get a little bit harder since you are higher levels and you don't hit a lot.
Before I go ahead into the job change part of this guide, I would like to talk about jobs, money, and upgrades.

In Flyff Penya, there are 4 basic jobs. The 4 basic jobs are Acrobat, Assist, Mage, and

Mercenary.

Acrobat - Uses YoYo, and can use bow and arrows. Yoyo can knock back enemies (not very strong)(Attack fast)

Assist - Uses stick or knuckle, With stick you can heal/buff people and knuckle you attack with.

Mage - A basic magician, can cast various spells and do a lot of damage. (Weapons say slow, but that's listed for melee attack speed.)

Mercenary - VERY BORING during the beginning and mostly relies on an assist's buffs at low levels. At higher levels, they become strong. (attack - Fast - Very fast.)

Job change

By now you should have decided to what you want to become in Flyff Penya. If you haven't, look above.

Mages - The mage trainer is in Saint Morning and you need to go to the magic shop to buy a blinkwing to go to there. (Eastern town part)

Assists - The assist trainer is in Flaris and should be easy to find.

Mercenary - The Mercenary trainer is right by the Assist trainer.

Acrobat - The acrobat trainer is in Darkon right next to where you teleport to after using a blinkwing.

Level 15-20:

So, your level 15 and you want to know what to kill, rather you should kill Feferns still or go on to those weird named Sleaze cats (Nyangnangs). Well as I said in the last part, if you kill things the same level as you, you will not get good exp, infact, it will reduce by as much as 50%! The right thing to kill is a Nyangnang in that case.