Optional Dresspheres:

Alchemist: Chapters 2,3 and 5. Complete mission Clean Sweep in the Calm Lands. Clasko will give you the sphere.
Berserker: Chapter 3. Complete mission Secure the Agency in Macalania Lake.
Dark Knight: Chapters 2,3 and 5. Ungerground Bevelle, just before reaching Limbo, there are some stairs reaching down to the sphere. You may need to do some work on the platforms to trgger the steps.
Full Throttle: Chapters 1 and 2. Talk to Tromell four times in Macalania Forest (Spring)
Gun Mage: Chapters 1 and 2. Complete mission Shave the Hypello.
Lady Luck: Chapters 3 and 5. Win the Sphere Break tournament.
Mascot: Chapter 5. Achieve Episode complete in all areas.
Samurai: Chapers 3 and 5. In Kilika Temple during the Pest Conrol mission.
Trainer: Chapter 3. From Kimahri. You must of responded with;
"You will have to learn to deal with these things"
"You have to figure this out on your own"
If you didnt pick these, if you have spoken to him three or more times he will still give you the sphere.


Hope that helps. But yes guides are a huge help.