In Gaias Retaliation you only get experience from creeps/monsters as long as they are in a range of -4/+4. So if you are a level 10 Squire you will only get experience from monsters level range of  6 ~ 14.

Quests on the other hand have a range of -5/+5.  Each quest that you pick up in Gaia will have a number in ( ) upon grabbing. So if the quest was a level 10 quest (10) the hero would get experience as long as they are within 5 levels of the quest i.e. level range of 5~ 15.