What is the Jackpot System?

Jackpot license, which can be purchased at fixed price from market, will activate the Jackpot System.
While under the affect of this license, all your loot items will be accumulated into an item obtain window. In this window, you can press two buttons: Collect all or Jackpot challenge.
Collect all -> you just obtain your items into your inventory
Jackpot Challenge -> you can select an item. After you have selected an item, if you click on the “Jackpot Challenge” button, you can acquire the item that you have selected as a bonus.
Depending on values of sacrifice items, you can obtain extra amounts of the selected item.
If you don’t have enough inventory space, the items will be mailed to you.
Maximum number of obtaining items is 99,999 even if the value of the sacrifice is greater.
Maximum number of items in Jackpot menu is 12 and maximum amount per item is 10,000. If you go over the maximum amount, item will go into your inventory.
Quest items and few other items will go into inventory not in Jackpot window.

How to Start:

Go to Town>Market and type in Jackpot. Buy the license and use it with your main character. You can now use JP for the next 24 hours.

Jackpot License [BEG] = 30,000
Jackpot License [INT] = 300,000
Jackpot License [ADV] = 1,800,000
Jackpot License [PRE] = 3,600,000

Beginning Steps:

Essentially, you must first experiment. Grind on a mob and JP every item they drop. After writing down the amounts for each item, go and check the market prices for all the items. Then stock up your JPs. Grind a long time and store up the items.

Like say I want Big Slabs of Lumber. I'll stock up loot like crazy and wait. The item amount generated seems to depend on 2 factors. The amount of the item I'm trying to JP for and the amount and quality of the other items in JP. If there are equip boxes, you'll gain much more than if there were only other items.

Those are the basics to making money with JP.

Items that you can not Jackpot:

Mercury
Secret Material Chest
Bonus Monster drops, i.e. Old Treasure Chest
Keys
Quest Items
Dragongod's Wishstone
Red and Blue Enchant and Crystal Boxes
7 Day Merc. License
Independent/Guild/Nation Dungeon reward boxes
Special boss drops, i.e. 3 Headed Dragon Ring, Hydra's Poisonous Gland, Fallen Power Ring, etc...

Some in-depth info:

Every item also seems to have a pre-determined value. When that item is JPed, it uses the value. The lower the value, the less it contributes when you JP, but, if it's value is low, you'll also gain many of that item if you JP. High value items have high numbers, so they help generate a lot of items, but they also need a lot of sacrifice items to make. The predetermined values do not correlate to market prices in any way.

There is also a random multiplier in game. All jackpots will give the same amount of items, if you ahve the exact same materials, but there is a random multiplier that will either decrease your over-all value or significantly increase it. This multiplier ranges from 10% to 200%. In other words, you can gain only 1/10 of the items you should be getting or 2 times the amount you're supposed to get.

The basic thing to avoid is trying to get equip boxes with JP. You'll usually lose out. If you want to gamble for equips, it's best to fight at least 10 times and JP it all at once rather than JPing it one by one.

An almost Universal truth for the JP system is that if the item is bad to JP, then it is good for sacrifice.

FAQ

1. Do the items in the Jackpot menu stay after the License runs out?
-Yes, the items stay in the menu and will remain there until you Jackpot them. No new items will be added to the menu. You can purchase a new license to allow more items to enter the menu.

2. Do upgrade Crystals Jackpot well?
-Yes, Giant Crystals and the like Jackpot well. 4 Volcano Valley Box and 1 Conqueror Box typically give 150 Giant Crystals.

Tips and Tricks:

1. Items from treasure Chests are Jackpottable, i.e. Growth Vial [ADV], Gilgamesh Sword Shard, and Still Beating Heart from Ornate Treasure Maps can be put in the Jackpot menu.

2. Store up items. If you JP immeadiately after a fight, you'll make significantly less than storing up items before JPing.

3. If you're a high level, then Goonzu World and the ID dungeons will give you many boxes for your Jackpot menu.

4. Jackpot Menu manipulation Trick

-1.Party up and set loot to leader.
-2.Look up all possible drops that can go into the JP system for the area you're hunting at.
-3.Fill up the party leader's inventory.
-4.Make sure the items in the inventory are the loots you don't want from the area you're hunting in.
--Example: I'm hunting silk, but the mob I'm hunting also drops leather. The mob only drops those 2 items. The party leader fills up his inventory completely, but makes sure he puts leather in one inventory slot and makes sure he has no silk in there. Now, whenever we party fight and loot, he'll get every other item, but I'll get all the silk.
-5.Go hunt for your items.

-Basically, an easy, but time consuming, method to make sure you fill the JP with only the items YOU want. Also annoying because you must actually find out what items and mobs are in one specific area and must correctly pack the Leader's inventory with all the drops you do not want and pack his inventory to FULL. I've done this to get Dragon Crystal in first slot for JP and fill up the other slot with boxes and other valuables from Goonzu World, all while filtering out the crappy stuff.

Thanks to Promethus for the contribution, the original can be found here