Fire Emblem: The Sacred Stones/Chapter 1: Escape!

Seize the gate
Have Eirika take out the Fighter near the starting point, then wait for Franz and Gilliam to arrive. Once they do, have Eirika join Gilliam in the middle of the map and have Franz go to Seth near the starting point, because a group of enemy reinforcements will arrive there. Have Eirika take on the two Fighters in the southwest corner, and use Gilliam to attack the two Soldiers near the gate without leaving him next to Breguet. Then, have Seth and Franz join the others at the gate.

Boss: Breguet
Take a look at Breguet's attack and Eirika's defense, keeping in mind that he'll get a bonus against her because of his lance. If you think Eirika can take him without getting killed, do so, and rescue her with anyone if necessary. Also remember that Erika's Rapier also gets a bonus because of its effectivity against armor. If not, try using Franz, who Breguet won't have an advantage against. If worst comes to worst, use Gilliam, who can definitely take a few hits. Breguet is slow and inaccurate by definition of his class. Erika may dodge his first attack. If so feel free to let Breguet attack Erika to allow her the experience. After completing the map, you'll earn a reward of 5000G.