If you were lucky enough to acquire Nerubian Slavemaker
from Four Horsemen Chest
you will use either of these bows throughout the entire leveling process to 70 and they will even be good enough to get you through your first Karazhan
while you work towards your Pre-Raid BiS option.
Below in the following table we will focus on options geared towards Hunters that either did not play/raid during Classic or are fresh rerolls to the class. There are not all that many upgrades throughout the leveling process and your main upgrades that you will want to use come from dungeons throughout leveling.