After using the ancient technology in Thor, you arrive in the town of Miguel.
Buy a Large Food Sack from the woman next to the item shop. You can now carry 22200 units of food. Now your food sack probably has enough room for all of the food that you are currently carrying.
Don't buy new weapons or armor right now, but buy any items that you need. If you have any of Cless/Cress's old equipment, equip it on Chester. If not, buy some equipment for Chester.
Be sure to equip Cless/Cress with a non-elemental weapon, like the Mecha-Halberd.
If you didn't get the Eruption spell before, you can get it now from a woman in the weapon shop.
Go to where Cless/Cress's house used to be, and talk to the teacher to buy a new skill. If you didn't get Mecha Blade before, go to where Chester's house used to be and check the drawers to get it.
Go to the formation menu and put Chester in your party so he can gain levels. He is still at a very low level compared to the rest of you. Equip him with a Black Onyx or two to raise his HP.
When you go through the mountain pass, take the northern path, and try to protect Chester from dying all the time. Open the chest in the northernmost part of the mountain pass to get a Reverse Doll.
Go into the Euclid castle. Approach the king and queen, and accept the money.
Buy food here, but don't worry about filling your food sack.
If you don't have Jet Boots, buy them. Buy one or two Holy Cloaks if you can afford it.
Don't enter the tournament at the castle yet. You probably aren't strong enough yet.
Leave town. If you need to rest, go to Bart's old house. Go north to Venezzia.
Go to the eastern side of the dock and talk to Harrison.
After the cutscene, go south from Euclid and go through the mountain pass again. Go southwest from there to find Morrison's house south of the mountains. In Morrison's house, rest and buy items if you need them. If you don't have Jet Boots, buy them. Then go to the cave next to the house to reach Volt's Cavern.