The game doesn't tell you any of the special effects on most of the equipment. So here is a list of Items what you usually pick up during the run and the reason why you actually do that:

General Equiment

• Jute Helmet - Immunity to confusion & Instant Death
• Pearl Brace - Immunity to paralysis & reduced Fire Damage
• Anger Brace - Immunity to Sleep
• Undead Ring - Physical Damage gains Holy attribute & Instant Death Immunity
• Seethru Cape - All Immunities except Instant Death
• Ghost Ring - Immunity to Instant Death
• Fury Ribbon - Immunity to Sleep
• Ghostclothes - Immunity to Confusion
• Camu Armor - Immunity to Poison (+Small Atk/Str Boost for Guy)
• Zirco Rod - Effective against Tank (“Hard” Elemental)
• Flying Axe - Effective against Flying (Gargoyles and Fire Dragon)
• Thunder Ring - Doubles Thunder-elemental Damage (Flash/Bolt/Thunder)
• Ice Ring - Doubles Ice-elemental Damage (Gale/Blizzard/Ice Valk)

Maxim Only Stuff:

• Pearl Helmet - Immunity to Confusion
• Pearl Armor - Immunity to Poison, Instant Death and Paralysis

You also get the Pearl Shield (Immunity to Silence), however, its terrible compared to the Zirco Shield (Berserker IP Move to increase Attackpower)

For a more detailed List visit this Guide: https://gamefaqs.gamespot.com/snes/588451-lufia-ii-rise-of-the-sinistrals/faqs/33113