If you want to be a spontaneous casting pixie, sylph seems the way to go. Sylph are from Monster Manual II and were assigned an LA in the 3.5 update booklet. They have 3 racial HD (outsider), +5 LA, casting as a 7th level sorcerer, improved invisibility at will, fly speed 90 feet, small size, -2 str, +2 dex, -2 con, +4 int, +6 wis, +6 cha. If you take sorcerer levels, you add them to your racial sorcerer casting, so you're only 1 level behind on casting.