In order for support gems to enhance the various skill gems, they must be placed into items. All slots in each item are considered 'linked' to each other. In normal Path of Exile, two handed weapons and chest armor have more sockets then normal, but I have an issue with this for tabletop games, so instead do this.
All weapons and shields get 3 slots, and all armor gets 2 slots. Two handed weapons get 4 slots.
Items that are especially rough have all red sockets, thief style gear gets green sockets, and witchy wizard items get blue sockets. Anything inbetween any of the two categories gets 50% of its sockets as each color. Itmes with odd numbers of sockets have a random socket to determine it.
Chromatic Orbs let you change the color of one item's socket to any other color you want.
Jeweler Orb lets you add one socket of appropriate color on any item.
Orb of Binding binds two items together to share all their sockets and gem connections. Cannot use any of the gems in one if the other is separated and not equipped with the other.
Strength Support Gems – 1d4
 Blood Magic- Lets you use gems without mana, each mana point is instead deducted from health. Still costs +1 mana or health every time you use the supported power.
 Totem- Lets you chance the caster of any skill gem or attack gem into a totem which is summoned at a location you choose within 30 ft. The totem casts the spell or uses the attack on the nearest target.
 Melee Splash- Supported gem 'splashes' 50% of its damage to enemies adjacent to the target.
 Ruthless- Increases the damage die size of all damage die the supported gem deals.
Dexterity Support Gems – 1d4
 Additional Accuracy- Add +2 to the to hit rolls with gems linked to this one.
 Chain- If the attack or spell strikes a target, it can chain to another one, once per chain gem. All enemies get the same defense against the gem power as the first one did, and any evasion or successful saves break the chain effect.
 Trap- Changes the skill gem's effect to activate on anyone who steps on a trap you place. The trap appears as a floor tile, a pile of leaves, or some other subtle indication.
 Faster Attacks Support- Lets you make two attacks of the supported gem each round, paying full mana cost +1 per attack extra with this gym.
Intelligence Support Gems – 1d4
 Blasphemy- Whenever you curse an enemy, other enemies who sense the first one getting cursed must make a save vs magic or also get cursed.
 Elemental Damage- The supported gem deals an additional +2 Fire/Electric/Lightning or Chaos damage. The type of damage it adds is random and determined when it is first found.
 Increased Area of Effect- All spells and skills are increased by other 5 ft, an extra target, or an increased sense range. (melee to within sight range, sight range to all within shouting distance).
 Cast when Stunned- When you are stunned, knocked prone, or otherwise incapacitated the skill will go off on the nearest applicable target. Costs x2 mana, doesn't activate without mana.