Every imperial soldier drops some gils and/or potions. The same you can steal from them
In the hall where you begin collect every single treasure, save you progress and continue forth.
Here along with Balthier you'll have to face three Seeqs. Every seeq has a different level, and they are: lvl 6 - 158HP, lvl 7 - 142HP, lvl 8 - 232HP. The last one has also the protect status on. During this battle you don't have your weapons so you'll have to handle the enemies without them. They all vulnerable to Fire so if you taught Vaan to use it there's no problem, if not use the Knots of Rust, which you probably found in the hall earlier.
After the cut-scene you continue the game from warehouse. Here you regain your equipment and obtain the map of these dungeons. Save your progress and continue. In the next hall many battles with imperial soldiers awaits you. Watch a guard near a pillar on your radar. If he goes away from you quickly run forward on up the stairs in front of you.
Upstairs kill Imperial Marksman on your left. Now run in the opposite direction and kill Imperial Hoplite and Marksman. Now get down and kill all enemies there (if they hadn't already come for you upstairs). Collect every treasure in here and go to the other hall. Here dispose of all the soldiers in here, just be careful not to attract too many of them at the same time. When that's taken care of continue to exit [screen 2].