Mage Armor:
Mage armor
Lower Reagent Cost
Lower Mana Cost
Mana Regeneration
Mana Increase
Resists
Luck
Warrior Armor:
Resists
Luck
Stamina Increase
Hit Point Increase
Mana Increase
Lower Mana Cost
Mage Weapons:
Spell Chanelling
Luck
Damage Increase
Swing Speed increase
Defense Chance increase
Hit Spell (Magic arrow, fireball, harm, lightning)
Hit lower defense
Warrior Weapons:
Damage increase (DI)
Defense Chance increase (DCI)
Hit chance increase (HCI)
Mana leech (ML)
Hit spell
Hit lower Defense (HLD)
Hit lower attack (HLA)
Swing Speed Increase (SSI)
Mage Jewels
Faster Casting (FC)
Faster Cast Recovery (FCR)
Lower Reagent Cost (LRC)
Lower mana cost (LMC)
Luck
Spell Damage Increase (SDI)
Stat Bonuses (Str, Dex, Int)
Defense Chance Increase
Warrior jewels:
Stat Increases
HCI
DCI
DI
Attribute increase (Hit point, mana, stamina)
Luck
Shields:
Spell Chanelling
Defense Chance Increase
Hit Chance Increase
Self Repair
Luck
*** This is a VERY general explanation, and any variation of these properties is good, obviously the higher the better. My favourite part of UO is the customization of each players characters, so you could put a completely different suit of armor on a character and completely change their strengths/weaknesses. Its best to just pick up most things with favorable (Ones above) mods and sort through it when you know what you need.
You will find that a large majority of the best armor, weapons and shields (excluding cleavers, bows, butchers knives and other tinkering/carp items) is crafted by players using Runic Kits. Ideally, you want to keep a massive eye out for jewels, bows, cleavers if your hunting.
Hope that helps