It might be helpful to brainstorm by sections.
Section 1: "Normal" adventure/survival/camping gear
This section depends how much stuff people would need to carry just to make a trip. This includes money objects of various kinds that the hunter would need in different regions.
Section 2: Monster detection gear
Stuff that the hunter uses to locate/track/uncover monsters. Consider whether monsters would hide, or do they just show up? Do they have lairs? are the lairs hidden? Can normal people see the monsters? What does the hunter have that allows him to see them or know where they are? Do monsters need to be summoned? Are there items required to open gates to lairs/crypts?
Section 3: Monster trapping gear
Stuff used to trap or set up traps for monsters. Does the hunter need to capture monsters? How would he subdue the monster and bring it back? Does the hunter need to stalk the monster and wait for it to appear? Can the hunter normally defeat a monster in combat? If not, how does he weaken the monster before a fight? How many monsters would be too many for the hunter to fight at once?
Section 4: Defensive gear
Stuff that protects the hunter during a fight. How do the monsters attack? What can block or weaken monster attacks? What can help the hunter escape if there are too many monsters to fight?
Section 5: Assault gear
Stuff the hunter uses to attack during combat. What weapons does the hunter use? Is the weapon the same kind that could be used against human? Is the weapon unique? Did the hunter design it himself? Do all hunters so similar weapons that distinguish them from normal warriors? Does the weapon designed to fight against one monster, or a group of them? Does the weapon use ammo?
Section 6: Communication gear
Stuff the hunter uses to communicate with other hunters, his boss, demons, or other factions, etc. What is the social status of hunters? Do they have special privileges? Do they need to carry licenses? Are hunters competitors? Do hunters have factions? Do hunters kill one another? How does a hunter know if another hunter is in his faction?
Section 7: Keepsakes
Stuff that the hunter keeps around for spiritual or emotional reasons.
Section 8: Loots/trophies
Stuff that the hunter is meant to collect from the adventure/monsters.
Section 9: Pets
Pets/horses/companions or other interactive beings that go with the hunter.