The main use of jackpot is for getting a mass amount of a certain item.
Never jackpot a box, it doesn't jackpot well.
First get the item you desire, such as torn pages for example. Its ok if you fill a few slots that aren't boxes, then bail on the dungeon. Now you need to fill your jackpot with good boxes.
Here are bosses that drop Conqueror boxes at a good rate.
Sedna - Adlivun's Center key required
Infinite Cube - requires oblivion to be open (Second and final floor)
Constantinus XI - requires byzantine royal key
Machine gun brooks - requires secret office key
Crazy Lord - requires marksburg castle to be open (Final floor)
Please note all these are high level bosses only recommended for 105+ that are well geared.
Freezing equipment boxes at a good rate.
Reckless control system - waste depot key required
Sedna - Adlivun's Center key required
Machine gun brooks - requires secret office key.
Heart of Eternity - requires oblivion to be open (Final floor)
For Divine boxes at a good rate.
Giant beast of madness - Bullman's room key
Heart of Eternity - requires oblivion to be open (Final floor)
Please realize the purpose of killing those bosses is to get the box in the jackpot slots and not to farm the bosses for getting your box count high.
Now you can start doing your individual dungeons and try to get some volcano valley boxes, osiris and pyramid boxes. They drop frequently in there unlike the conqueror, freezing and divine. Remember do your individual dungeons the second you have the chance they are a massive source of all the boxes you pick up. And do as many guild/nation dungeons as possible.
I would recommend jackpotting your item once you hit 50 conqueror's boxes, 5-10 divine boxes, 20-40 freezing. You will get at least 30k pages.
Please remember jackpot can either screw you or make you a lucky bastard.
Please note this can be done with any item that has the same value as torn pages. It can be done with other items such as phoenix feathers but the amount you will get is less than torn pages.