[qq]-WHO'S THE IMPORTANT CHARACTERS? (i need more than yuna, rikku, and paine) [/qq]There's Buddy, Brother and Shinra, a trio of Al Bhed who are the other half of Yuna's Gullwings team. Meyvn Nooj, Gippal and Baralai are the young male leaders of Spira's three major political groups.[qq]-Who's the villians this time?
[/qq]The first major opponents you'll face are Lady Leblanc of the Leblanc Syndicate, a Sphere Hunter group that rivals the Gullwings. She's capricious and dangerous, with a sharp tongue and a wit to match. Her weapon of choice is a strange one: a hand-held purple fan. She had two henchmen, the lanky gunslinger Logos, who's smart and sarcastic; and his counterpart Ormi, a stocky brawler whose only equipment is a large shield.

There are, however, other villains in the game, more deadly and surprising than the ones listed above. However, to describe them would give away so much about the plot.[qq]-What's a dress sphere?
[/qq]Dresspheres, like TasteyPies said, are the game's way of letting you change a character's 'job class', just like the crystal shards in FFV. Dresspheres are a lot like the other spheres that played a part in FFX - they're small crystal orbs, made from the energy of life, and capable of carrying all kinds of information - words, images, even thoughts and memories. A dressphere lets the user take on the appearance and characteristics of the person whose traits are burned into the sphere. For example, the sphere carrying a Black Mage's spirit transforms the character's appearance and abilities into those of a Black Mage. There are over 15 dresspheres in total, plus some particularly special ones...

It's good that you're looking for info before buying the game, but it'd be wise not to ask too many questions. There's not much that's worse than accidentally ruining big surprises by delving too deep