Gilder > Information
Here are strategies for the bounty fights that Gilder can take part in...Note that these are SoAL only.
Rupee and Barta
This fight is pretty straightforward... Make sure Aika uses her Delta Shield to block Rupee's magic. Hopefully you have a few Crystales or Crystalum boxes with you. The only s-move worth using here is Cutlass Fury...everything else does very little damage.
First, and most important, is to set weapons to purple. Then, while Aika does her shield, have everyone else use the box or crystal-es/um spells on Barta ONLY. This is important as, if you damage Rupee, he can use more powerful attacks. Barta is somewhat predictable in his attack, and if he charges, you can easily tell that character to defend. After Barta falls, keep that Delta Shield up and Rupee isn't even a bother. A few more attacks and victory is yours.
If you have prophecy for this fight, by all means go for it. I didn't dare risk Rupee's wraith though, so I can't tell you how well it works.
Loose Cannon Lapan
He must be fought after obtaining the Delphinus, but if you wait long enough, you can get Gilder back to help ;)...but although I hate saying this, I think you'd be better off with Enrique for this fight since Justice Shield can help a TON when he uses his really powerful attacks.
Basically, have everyone focus, healing when necessary. Usually, he'll attack the same character as his helpers (forget their names), so have that character defend, healing with crystals to save SP. When you're maxed, let that prophecy rip. That plus a few more attacks will beat him, no real problem.
Ixa'ness Demons
These are some tough ladies. Most important I think is equipping Fina with an item to prevent confusion. Have everyone else focus and heal when necessary. When you're close to max, have Fina use Lunar Cleansing to clear all status ailments, and then you're ready to prophecy. One prophecy should take them all out.
Alternately, (and you ARE using Gilder, aren't you?), you can use Aura of Denial and just prevent all status changes. How nice! Have everyone else focus and have Fina use healing crystals when needed. Then, just prophecy and you've got it.
Vize
By far the most fun fight in the game. Vize tends to use Cutlass Wraith or Revenge (like Cutlass Fury and Counterstrike), Anita uses Anita Burst, Anita Shield, and Quika (like Lambda Burst and Delta Shield). Fiana uses Drilnos and other attack and support magic. The easiest way to beat them is a prophecy, but getting there isn't easy. The first few turns you're almost guarenteed to be safe, so have everyone focus, and have Fina use Lunar Winds when necessary. Delta Shield is also nice to have after the third turn to negate Fiana. Keep your health up with Gilder and Fina (crystals) while Aika uses Delta Shield and Vyse focuses. Most likely someone WILL die, so have riselem crystals with you. Both Sacrum and Sacrulen crystals are vital for this fight. As long as a character is defending, he/she can survive Cutlass Wraith. Once you get to max SP, a prophecy almost takes them all out. Fiana can be taken out with a single Cutlass Fury or a few normal attacks, Anita with a few more than that. Vize alone is no problem at all as he only attacks one character. If you get that far, just use Cutlass Fury, healing when necessary. Before you know it, your name will be cleared.
Daikokuya the Wealthy
One of the strangest combats ever... Daikokuya (who will henceforth be refered to as "Daku"), is a wimp so he wants at least 3 bodyguards. If there are less than 3 Boos, he will use "Bodyguard," which is a free turn for you to attack. The Boos will use mainly normal attacks, which you can survive no problem (at this point, I had 2 Defensive Auras, which makes the wearer take 0 damage from all normal attacks, if you have these, USE THEM!) They also have endless pockets of Sacres Crystals, which they almost always use to heal each other (only once did they heal Daku). Daku also has a "Golden Flurry" attack that damages all party members and can confuse. He also has Eternes, but it never hit for me. His Electrulen is also weak. That said, this battle really isn't too hard. Have Vyse and Aika focus while Fina uses healing when necesary and Gilder does his Aura of Denial. If you need more than one healer, fine too :D Let a prophecy rip. It will take about 3-4 prophecies alone, or you can damage Daku to about 1/4-1/5 health before prophecying to kill everything at once.
As for the final one...I'm not there yet :P I'll let you know once I fight it.