Yeah, the problem might be a RAW thing about the MM1 feats; it's like saying I have the strength necessary or feats while equipped with a belt of strength.
You qualify for any feat, skill, prestige class, spell level, etc., that you meet the prerequisites for, regardless of where those prerequisites come from, unless the thing you want
specifically says otherwise. This means if you had a 14 WIS at level 15, but were wearing a +4 Periapt of Wisdom, you would have 18 WIS and could therefore prepare 8th level spells.
And like everything everywhere ever in 3.5, if you lose access to a prerequisite for something then you lose the benefit of that thing until the prerequisite is restored.
Note that forest gnomes don't speak common by default, and you will have to spend a bonus language or skill points on it.
You could craft any wondrous item for which you could prepare the necessary spell. At a quick DMG glance that would be:
Amulet of Health,
Amulet of Mighty Fists, Amulet of Natural Armor, Bag of Tricks, Belt of Giant Strength, Boots of Striding and Springing, Boots of the Winterlands, Bottle of Air, Cloak of the Manta Ray,
Cloak of Resistance, Cube of Frost Resistance, Darkskull (might cause alignment problems),
Decanter of Endless Water, Dust of Dryness, Dust of Tracelessness, Elemental Gem, Elixir of Vision, Gauntlets of Ogre Power, Gauntlets of Rust, Gem of Brightness, Gem of Seeing, Gloves of Dexterity, Gloves of Swimming and Climbing, Goggles of Minute Seeing, Helm of Underwater Action, Horn of Fog,
any Ioun stone, Keoghtom’s Ointment, Lens of Detection, Mantle of Faith, Orb of Storms,
Pearl of Power, Pearl of the Sirines, Periapt of Health, Periapt of Proof against Poison, Periapt of Wisdom, Periapt of Wound Closure, Pipes of the Sewers, Robe of Eyes, Golembane Scarab,
Silversheen, Slippers of Spider Climbing, Unguent of Timelessness, Druid's Vestment, Wind Fan