Blue Dragon

Basically, Moody Dragon is hardly an appetizer. The best time to tackle them is just before you fight Nene. It involves building up a couple of your classes so your characters have the best set of skills equipped so battles are not as tedious. Here's a few recommendations:

-If one of your mages has the Barrier Mage Class unlocked, work to build it up to rank 50 (which will involve a lot of SP) to unlock Field Barrier 3. Have this same mage equipped with the Regenerate MP skill. Basically, you'll have a barrier that can tear through most defeated enemies (turtles, flying types, and large machines for example cannot be caught in the barrier even when defeated) and have you earn 1/2 their standard SP total for virtually free! If you have any Black Belts, equip them since the Double SP ability they afford works in and out of battle.

-Get Barrier Mage class to level 50 and learn Field Barrier 3 (can be done quickly with a Black Belt on the char, Regenerate MP makes it free to use, and go to the Laser Field. From the warp/save point, go down the main path and turn left, going in the general direction of Baroy Town. Go past the large rock (where the lazy bear is standing guard) and go down the right enclosure where the chest in. This is an area where countless flying moles will spawn while you run around. In this area, Black Belt + Field Barrier 3 + Regenerate MP = 4 SP per kill for free very quickly.

-For your fighters, learn the Assassin's Double Strike and Agility skill, max out the Sword Master class. For your mages, Black and White magic are a must, along with the Support Mage's Double Cast (rank 35). Guardian class maxed out is also a plus too since Berseker + Endure + Total Guard will ensure that your prime attacker who has a huge amount of HP will be able to take constant physical blows in place of others, and if his HP falls to 1, he can spend MP in pace of losing that one last HP. And as a result, Berserker will amplify his attack considerably, and Double Strike will help greatly. Even Absolute Counterattack on the defender will guarantee a hit each time he is hit.

Here's the general strategies for each dragon (according to what I found out):
-Blizzard: water protection is a must, use Previve and Shellus on your chars. One effective strategy against the dragon's magic resistance (since it'll use Reflecta and keep your spells hindered) is to bounce Refleca-reflected spells off of YOUR OWN CHARS! Cast Reflecta on your chars and bounce magic off of them, keeping track of their reflect shields. Or you'll fry your own char to death.

-Amethyst: weak to wind, and they use wind attacks (wind resistance is a must). the dragon has a nasty attack called Lightning of the Gods. A Total-Guard equipped fighter will catch it every time and protect your other chars, but make sure he has Previve cast beforehand.

-Spark: Uses wind and is weak to it. It does keep using Black Wind to hit 4 of your chars for damage and for whomever has wind absorbing gear equipped, heals them. Just pummel it with spells and keep your HP high.

-Phantom: uses wind and is weak to it as well. But, you cannot use any physical attack against it (including Corporeal attacks!). Instead, use magic and magic sword attacks since these will still damage it.

These are basic strategies, but know that its best to have learned all the skills for Assassin, Monk, and Sword Master for your fighters (with Guardian a definite plus) and Black, White, and either Support or Barrier for each of your mages.

Another thing you can do when the Blizzard Dragon casts Reflect on itself is bounce Zephyr off the dragon on to your characters for some quick healing AND nulling the spell; twice the benefit that way and less work.