There are so many items I don't really know what to say.
The ones in 装飾1(Accessories 1) are 'Berry' items that can be used only once per battle. They have many assorted effects.
They do come back after battle, so you can actually heal a doll's status effects at no cost, by giving the right 'berry', then just sending it out to battle.
But the game tells you this on a sign in front of a cave you can reach only after defeating Medicine.
治癒の符 heals all status effects. (Rather, that's what the description says, so I don't really know if it's true. But I'm sure it's true)
The ones in 装飾2(Accessories 2) are normal hold items.They have many assorted effects.
必殺の極意 boosts damage of super-effective attacks.
兵糧丸 heals the holder by a little bit at the end of the turn. Sadly, battles can end before the turn ends, so one-shotting every wild doll will result in no healing.
双眼鏡 boosts accuracy by a bit.
The 髪飾り series boosts a particular type's damage by 20%, which can be useful.
On the items menu, you can press Shift, then select yes to sort the items, which tends to group together items with similar effects
The only thing I'd look out for would be 戦闘の教範(Training Manual), in 装飾2. A doll that holds this item will receive 50% more exp.
Kanako gives you this, and you can get one more in the cave behind Hakurei Shrine, but by the time you get the second one you've almost beaten the game.
Almost every item has a pokemon counterpart. Which would be helpful if you played pokemon. But some of them come from newer generations.
If you need them, I can tell you what every Accessory does. Although I'd rather not. It might collide with current translation efforts.
By the way, Power Aya one of the dolls which is just wrong. Wastes too much time.