After finding Ilchymis, you can have her on your ship. Return to Crescent Isle, so that you can give her some money. She will build a boutique for you. The next time you return to Crescent Isle you will be able to buy items from her. From now on, buy all the items she has and give them to your party members and to Vyse. After the first session of buying things for your party, go outside then return back in again. You can now buy the same items. Once again, load up your party then get out. Repeat this as many times as needed. Check the menu to see if you have 99-9999 of items on your party members. Go into a ship battle or ordinary battle with these skills. If the enemies will shoot a magic spell on your team, the points will be 0 and you cannot take much damage.