There is no such thing as too many items.
Weapons are equipment items that are the primary means of damaging monsters. There are six weapon types that are shared between the different character classes.
Ability Items are equipment that is specific for each class and can be used to activate a unique ability for the class. Abilities require magic points (MP) to use.
Armor is a category of equipment items that primarily increase the defense of player characters but often provide other stat increases and other effects as well.