Rest and save. Now, go to the easternmost house in Maia. There's a staircase leading to the door. Go inside and talk to the short Frenchman. This is Bon Voyage. He has a cannon behind his house. Talk to him and he'll tell you to go out back. Follow him and prepare to be disappointed. Yep, he needs gunpowder. But, where do we get it?
There's a bald NPC with a red beard in front of the inn. Talk to him, then head back to the Road. Go back to the Cleft of the Earth. The bald guy can't tell you this next part. Talk to the Silver Statue and use Wisp. The wall will open, revealing your new path. Go down the long tunnel. Take note of the walkways stretching across the stairs — you'll be running on them soon enough. At the bottom, follow the path to the dwarf village.
The dwarf village is a fairly awesome place. Go to the item shop and ask for Watts. Watts is the item shopkeeper, and he also has gunpowder. However, he's not there. Oh well. Go to the weapon shop and armor shop and equip yourself. Use your leftover cash to fill up on supplies, then rest, save, and head out.
Right outside of the dwarf village, talk to the dwarf digging there. He'll open up a new tunnel for you. Go inside. Follow the path until you see a dwarf. That's Watts. You can't get to him just yet. Go west and then follow the northern path. Keep going, and you'll find him standing in an empty room. Go to him and talk to him. He wants 5,000 gil for the Gunpowder. You almost certainly don't have that; it doesn't matter, because he'll run off again. Follow him. Keep on the path through the tunnels, and at the end, you'll find yourself in another room with Watts. Heal up, then talk to him to start the next boss fight.
Boss: Jewel Eater
This guy can be tough if your levels are low. However, if you're keeping up, you should be level 6, which is just fine for this fight. Jewel Eater is weak to Thunder Magic, but since you don't have any yet, just hit him with normal attacks. If you have Angela, use up all of her MP on Holy Ball. If you have any Assassin Bug Eyes, you can use them. Just keep hammering away and keep your HP above 70 or so. Jewel Eater's Magic list includes Diamond Missile and Defense Up. He'll begin to cast Defense Up when he is nearly dead.
After you beat the Jewel Eater, Gnome comes bouncing down and has a small story to tell. He then joins your party. Also, Watts apologizes and gives you Gunpowder. It's time to leave now — we're finally going to Forcena!