Items for increasing spell cells

[Mephisto]

I am interested in increasing amount of spell per level for my main hero mage. So I want to ask you of which items in BG2 can help me with this deal and where they are located)

I am jealous of Edwin has much more of spell slots than my hero)

[Armanz]

Obvious spoilers ahead:

There's a Ring of Wizardry or how it's called after you finish the quest in Lavok's Sphere.

[philos3]

More obvious spoilers.

There are two different Rings of Wizardry (I believe they have different names). One of them allows you to memorize 1 extra spell for spell levels 1-4. The second allows you to do the same for spell levels 5-7. There is the necklace of Metaspell Influence (found at the beginning in Irenicus' dungeon) that adds an extra 2nd level spell. Once your character reaches a high enough level (2,000,000 XP+) and can add "Quest" abilities, mages/sorcerors have the option at each level up to choose the ability to memorize an extra 6th, 7th, or 8th level spell (I think you have to take them in order).

[voehringer_nitron]

The one from Lavok is called the Ring of Acuity. It gives two extra second level, one extra third level and one extra fourth level spell.

The Ring of Wizardry is one possible reward from the Mage Stronghold quest, available after completing the Planar Sphere quest. You will be assigned three apprentices, and will direct them to enchant items for you. The Ring is in the third group of three items you can choose from.

You can get a Ring of Reaching from the Harper Hold (Galvarey Estate) if Jaheira is in your party. It should not be necessary to romance her. In the original disc-based game it was called the Ring of Wizardry and the description was the same as the one from the Mage Stronghold, which implied it was unique, and made little sense if your PC was not a mage/sorcerer. Both of these allow one extra fifth, one extra sixth and one extra seventh level spell.