Your equipment is already the best. Using up all greckles before fighting Slayer is a good idea; getting 60 more def reduces damage to 6k. If there are other gems you had not picked up yet do so and make sure you talked with people in Tar Mother room in Homeland.
Other improvements likely require restarting:
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×You want to use later machines as much as possible. None in Homeland, very few in The Goblin Tribe. Once you reach Pirate Lair can spend more freely since the difference between Pirate Lair and Preservation of Tueno machines is relatively small.
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×Use the Lucky Blade as much as reasonable. More greckles = more stats.