Basic Treasure Generation

Treasure

To determine the amount of treasure that can be found in a monster’s hoard or when you create a dungeon and have a treasure as a result
(see below the creation of a dungeon), roll 2d6 thrice by adding the level of the dungeon to each result. One is for coins, the other is for non-coins
treasures (such as arts and gems) and the last is to determine the chance of obtaining magical item. Outdoor lairs count as a level equal a level one.
Civilized treasure or stronghold treasure, such as a merchant’s loot, is equal to a level two dungeon. 

On a double, you can add a small magical consumable, such as a Dust of appearance/Disappearance, Potion of Healing, etc. 

2d6	Coins	Gems/Objects	Bonus on the Magic Item Type
2 - 6	Nothing	Carved Bone/Ivory/Jade Statuette (25 GP)
6	5d10	Small Gold Bracelet (50 GP)
7	10d10	Gold ring with a bloodstone/jade/turquoise (250GP)
8	5d10 x 10	Large well-made tapestry (250GP)
9	6d10 x 10	Silver chalice with moonstones/small diamonds (750GP)
10	7d10 x 10	Ceremonial electrum daggers with inlay (750GP)
11	8d10 x 10	Small gold/obsidian idol/statue (750 GP)	+1
12	9d10 x 10	Painted gold war/art mask (750GP)	+1
13	10d10 x 10	Fine gold chain set with a fire opal (2500 GP)	+1
14	5d10 x 100	Old forgotten masterpiece painting (2500 GP)	+2
15	6d10 x 100	Gold music box (2500 GP)	+2
16	7d10 x 100	Platinum bracelet set with sapphire/diamond (2500 GP)	+2
17	8d10 x 100	Jeweled gold crown (7500 GP)	+3
18	9d10 x 100	Jeweled platinum ring (7500 GP)	+3
19	10d10 x 100	Gold cup set with emeralds/diamonds (7500 GP)	+4
20	5d10 x 1000	Gold jewelry box full of smaller rings set with stones (7500 GP)	+5

To determine Magic Item Type, roll 1d20 + bonus. A creature with a huge lair, or a castle, etc. gives +1-3, according to the Referee’s whim. 

d20	Magic Item Type
1 - 19	None
20 - 22	Uncommon Magic Item
23 - 24	Rare Magic Item
25	Very Rare Magic Item
26	Legendary Magic Item

You could probably adapt the list of magical item according to your edition or system. Here is one I made for a game of 5th ed.

d12/d10/d8/d6	Uncommon	Rare	Very Rare	Legendary
1	Boots of Striding and Springing	Amor +1	Cube of Force	Holy Avenger
2	Cloak of Elven Kind	Boots of Levitation	Cloak of Arachnida	Ring of Djinni Summoning
3	Gauntlets of Ogre Power	Helm of Teleportation	Dwarven Thrower	Ring of Invisibility
4	Potion of Animal Friendship	Potion of Gaseous Form	Potion of Flying	Ring of Spell Turning
5	Potion of Giant Strength	Ring of Protection	Potion of Speed	Scarab of Protection
6	Rope of Climbing	Scroll (level 1d6)	Ring of Telekinesis	Magical Sword (+3)
7	Potion of Resistance	Staff of Healing	Rod of Absorption
8	Staff of the Python	Potion of Heroism	Magical Sword (+2)
9	Wand of Secrets	Wand of Fear
10	Non-Sword Weapon +1	Magical Sword (+1)
11	Shield + 1
12	Scroll (level 1d4)

Magical Swords are unique and legendary in their own way. According to their power level (+1, +2 or +3),
roll on the charts below, once for every column. They need a special name, a special look, a quirk, etc.

d20	Alignment	Type	Intelligence (+2, +3)	Language (+2, +3), only if Medium or higher intelligence	Main Power (+2, +3)	Secondary Power (+1, +3)
1	Chaos	Ice Brand	None	Common	Nothing	Nothing
2	Chaos	Ice Brand	None	Common	Nothing	Nothing
3	Chaos	Lightning Brand	None	Common	Nothing	Nothing
4	Neutral	Lightning Brand	Low (Empathy)	Common	Nothing	Detect magic
5	Neutral	Flaming	Low (Empathy)	Common	Clairaudience	Detect magic
6	Neutral	Flaming	Low (Empathy)	Common	Clairvoyance	Notes shifting wall and rooms
7	Neutral	Flaming	Low (Empathy)	Common	Telekinesis	Locate secret doors
8	Neutral	Magical Silver	Low (Empathy)	Common	Immunity to … (one random condition, including life drain)	Detect sloping passage/shifting floor
9	Law	Magical Silver	Medium (Speech)	Common +1	Teleportation	Detect sloping passage/shifting floor
10	Law	Magical Silver	Medium (Speech)	Common +1	X-Ray Vision	Detect traps
11	Law	Magical Silver	Medium (Speech)	Common +1	Illusion generation	Detect traps
12	Law	Magical Silver	Medium (Speech)	Common +1	Levitation	Detect traps
13	Law	Magical Silver	Medium (Speech)	Common +1	Flying	See invisible objects
14	Law	Magical Silver	Medium (Speech)	Common +1	Healing	See invisible objects
15	Law	Magical Silver	Medium (Speech)	Common +1, +1 Exotic	Dispel on hit	See invisible objects
16	Law	Of * Slaying (only has bonus against * type)	Medium (Speech)	Common +1, +1 Exotic	Antimagic field	Detect * creature
17	Law	Light (aka Sun Blade)	Medium (Speech)	Common +1, +1 Exotic	Can slice through plane	Detect * creature
18	Law	of Charm	High (Telepathy)	Common +2, +2 Exotic	Vorpal	Detect * creature
19	Law	Life Drain (alignment becomes Chaos if it’s not already)	High (Telepathy)	Common +2, +2 Exotic	Immunity to ESP and bonus against psionics	Light
20	Law	Cursed Sword (have the sword become stuck to the player until the curse is broken with a heavy disadvantage)	High (Telepathy)	All	Invisibility	Light

To determine the monster type of the * symbol in the chart, roll 1d8:

• 1: Troll
• 2: Lycanthrope
• 3: Vampire
• 4: Giant
• 5: Orc
• 6: Dragon
• 7: Psionics
• 8: Elemental

Then determine the use and history of the Magic Sword (inspired by DMG 5th). This can be also done for every magic items. 

d20/d8	Created by… (optional: reroll to determine “to destroy …” or “to gift to …”) d20	History d8
1	Aberration	Arcane
2	Human	Bane
3	Human	Heroic
4	Human	Ornement
5	Human	Prophecy
6	Human	Religious
7	Celestial	Sinister
8	Dragon	Symbol of Power
9	Elemental Air
10	Elemental Earth
11	Elemental Fire
12	Elemental Water
13	Psionics
14	Fey
15	Fiend
16	Giant
17	Undead
18	Undead
19	Machines
20	Unknown/Forgotten