Before start Arms master makes it so Half health needed for Phy Attack and the same with Spell master, but half SP for attacks.
Joker - Item that gives stats +7. (This makes it so that my physical and magic does more damage when I’m using Yoshistune or Izanagi-Okami.)
Morgana - Ring Of Lust (don’t really use Morgana, but I would put ring of lust, this makes it so that he’s even more of a healer then he already is, giving one teammate Attack up and heals)
My Boy (R) - Ring of Pride : the one that gives one person charge. (This is extra handy if your Ryuji doesn’t have Charge yet in NG+ or if you just rushed the game and don’t have it, but this charge also makes it so that you can give it to other team members, giving you more rounds to boost. You can also go to jazz club for Arms master)
Ann - Ring Of Greed : The one that gives Concentrate (Same reason as Ryuji, since she can give it to Joker and other teammates for 2x Damage! Also you can go to jazz club for spell master)
Yusuke : I don’t remember if there is, but any item that gives Ali Dance (As a main Physical powerhouse, you want to make sure that he hits harder then he already does his abilities, Ali Dance makes it so he critical more, making his more OP, and if you can get Arms Master from the Jazz club so he only receives half HP)
Makoto : I don’t really put any items on my Makoto, but a good item would be crystal item from the 6th palace, (This makes it so you can increase teammates defense (if you still have that move) and their evasion, also you can get spells master from jazz club)
Haru - I don’t use Haru enough to know
Spoilers below!!! (IF YOU HAVENT FINISH ROYAL, NOT GO DOWN)
Akechi - For Akechi, I recommend any Items that would make it so that enemies can’t really hit his weakness, makes Akechi nore efficient in battle and can easily destroy enemies. You can also use crystal from Final Palace for instant Knock down when you ambush,
Kasumi/Sumire - For this person, I recommend the same thing as Akechi, with the weakness resist. If you don’t have any more of this, I guess just use items that make them dodge, it crits and etc.