Just some random information about what item slots give what 2-piece set bonuses. This is for the Crabnaroks and Troves, not IA boxes. It's fairly easy to figure out, but I didn't see it broken out anywhere, so....here:

Helmet, Shoulders, Chest:
Token Boost - Currency and Token gain - 10% (Not Darkness)
Planar Bane - Increased Damage to Rift Creatures - 5%
Experience Boost - Increased XP - 10%

Gloves, Legs, Feet:
Noteriety Boost - Noteriety boosted by 10%
Mounting Speed Boost - Mount time reduced by 10%
Planar Ward - Reduced damage by rift creatures - 5%

Belt, Earring, Neck, Ring:
Lesser Endurance Boost - 1%
Greater Endurance Boost - 2%
Mighty Endurance Boost - 3%

Lesser [Main Stat] Boost - 1%
Greater [Main Stat] Boost - 2%
Mighty [Main Stat] Boost - 3%

Note: These are all BoA, so you can pass them around to alts and such as necessary. Cloth would make the most sense to collect for utility. The token and noteriety bonuses are nice. The 65 XP gear is useless today, but will be nice to have ready to go when 4.0 has a level bump.