Final Fantasy Tactics Walkthrough

After Dorter, this battle is a breath of fresh air.  You have two squads to set up this time add a Chemist or someone that can heal to the squad with Ramza, and bring along a Black Mage as well.  The last character can be anyone you want.

Making Ramza a Monk for this battle is handy, especially if you can get Aurablast, which can hit characters from afar.

However, another good strategy is to park two characters on opposite sides of the doors leading out from the building.  When characters come out to investigate and attack, they'll be hit from both sides and won't let anyone else out.  On Ramza and Delita's side of the field, there shouldn't be much action save one Monk, and Ramza's Aurablast will take care of him while allowing Ramza to run away after hitting him.

A similar alternative strategy is to use a tanking character like a Knight to block up the doorway for the second party, keeping them healed so that the first party can handle the enemy Monks and then pincer the remaining enemies.

This is another good battle early in the game to try to farm for treasure and crystals from the enemy, particularly if you can jam up the doors into the building with characters or corpses and pick away at the remaining enemies with ranged attacks. It's also a good time to diversify jobs some and start earning JP in new jobs, while keeping secondary abilities around from the jobs for which you already have made good progress. The guests and their AI-supplied bloodlust might make this trickier, but if they fall or are blocked outside of the building they will be out of the way.

Inside the ruin, there's some action brewing with the Marquis, Wiegraf, and Gustav.  Gustav thinks that kidnapping the Marquis would prove a point to the nobles of Ivalice that they're a force to be reckoned with, but Wiegraf argues that that's completely against the point of the Corpse Brigade and that level of violence will only cause more danger for the group.  Gustav refuses to listen, so Wiegraf pulls rank by way of sticking his sword in one side of Gustav and out the other.  Ramza, Delita, and Argath enter, and Wiegraf exchanges the Marquis's life for his own safety.  The Marquis is saved, and it's time to return to Eagrose. Don't forget to make your stops on the way to reequip or get equipment for new jobs you've unlocked over the last few battles.