There are a bunch of people in Koringwood who are cutting down the trees because people think it's magic wood and will pay a lot for it. In this battle, you are outnumbered. You would do well do have someone in your party who can inflict status ailments that will prevent your enemies from moving or attacking. It will be up to you to decide who the worst threats are in this battle. Keep your units apart if you can, to prevent the enemies from casting spells on large numbers of your group. Try to prioritize such that you focus on the easier kills first. The fewer enemies in the fight, the better. Be sure to check on the enemies to see if any have healing spells, because you should get rid of those quickly.