Sockets

Where can I put sockets?

Chest -3

Two-handed weapon - 2 or
Weapon -1 PLUS
Shield - 2 or Offhand - 1 or Weapon - 1

Pants - 2
Helm - 1
Amulet -1
Ring - 1
Ring - 1
Bracers - 1
Belt - 1

Max possible: 14 (weapon and shield) or 13 (other setups)

These break down as follows:

Helm 1 socket
Weapon 1 socket unless using a two-hander or dual wielding - 2 sockets
Other 11-13 sockets



Followers

Two-handed weapon - 2 or
Weapon -1 PLUS
Shield - 2 or Offhand - 1 or Weapon - 1

Amulet -1
Ring - 1
Ring - 1


In addition there is a legendary sockets affix that allows sockets on legendary Follower Special items (a special slot for Focus, Token or Relics).



Gem mods for Rank 14 gems

Helm +31% exp per kill OR +31% Gold Find OR +31% Magic Find OR +18% Life
Weapon +20 damage OR attackers take 50 damage OR crit damage increased by 100% OR each hit adds 300 life
Other +58 Strength OR +58 Intelligence OR +58 Dexterity OR +58 Vitality



Example


Level 60 Barbarian using a two-handed weapon and rank 14 gems:
+200% crit damage
+18% Life
+638 Strength.



Analysis

Helm mods

1. Experience. This seems really powerful. The affix on items that improves experience gain improves it by a set amount. The highest version is Savvy that gives +24 exp per kill. So increasing by a percentage might be really strong depending on the way this percentage is factored in. Even if it just increases the base amount it's a strong mod and an alt with this gem and a suit of savvy blues would be astonishingly quick to level. This will be of interest to D3 profiteers if and when selling characters is added to the game.

This bonus becomes utterly redundant at the level cap. It will however be extremely useful every time an Expansion raises the level cap.

2. Magic find or gold find. I would guess that magic find suffers from diminishing returns and gold find doesn't, or at least doesn't to the same extent. So if you're suiting up in both then gold find might be the optimal pick if you already have high levels of both. Otherwise take your pick for farming runs where the mobs aren't particularly dangerous.

3. + Life. Very strong for situations where the game is really challenging. These include starting a new difficulty, pvp and speed runs. If you're not worried about drops or leveling speed it's the only choice that actually improves your fighting capability.

Summary: Use + exp% until 60, especially since experience sharing has been reported not to work. Then gf or mf in easy runs, +life in hard runs.

Weapon mods.

+ damage. Virtually every character ability is based off your weapon damage so this is clearly very strong. It's a subtle advantage of two-handed weapons or dual wield that you can use 2 weapon gems which may be better than using 1 weapon + 1/2 other. There's a straight equation between whether adding damage directly to the weapon beats adding crit damage. In either case using two weapon gems gives a very large bonus: +40 weapon damage or +200% crit damage with Rank 14 gems. The fixed value for weapon damage may make that mod stronger with fast weapons than with slow weapons.

Attacker takes damage. Only useful for Fierce Loyalty witch doctors.

Each hit adds 300 life. I'll go out on a limb and say this is possibly useless. At high level you will have life leech and damage converts to healing gear anyway so using this gem over a damage increasing one lowers the amount you leech. So it's worth less than 300 since it penalises you some life per hit you would have got it you hit harder. Maybe 300 life on a dual wield fast weapons frenzy barb is so large that it offsets this but for most builds it's simply not worth sacrificing damage for this mod.

For an excellent opposing view look no further than MisterCurry.

Other mods

Simple. Take the stat that adds damage to your class or Vitality. Vitality is good if otherwise you would die so very strong for situations where the game is really challenging. These include starting a new difficulty, pvp and speed runs.