Spy is one of the most changed Traits in Season 3 with the removal of Kai’Sa, Kha’Zix, and the addition of 2 champions, Zed and Nocturne. To effectively utilize these Spy champions, we need to maximize their strengths.
Here are the strongest playstyles revolving around 7 Spy champions in this Season 3:
Kha’Zix

As the main carry in the Void composition, Kha’Zix is particularly hot in the current meta as it is about to… disappear in Season 3. The strongest playstyle for Kha’Zix is utilizing the Infinity Edge + Rapid Firecannon combo, combined with the attack speed of 2 Spies and the true damage from the Void, allowing Kha’Zix to “devour” the backline champions of the enemy team.
Nocturne

This new Spy champion is most commonly used in the Spy Pilot composition in patch 10.12. Nocturne needs to reach 3 stars to be reliable and equipped with items. Otherwise, the main carry in this composition will be Zed with 3 items: Death’s Dance, Giant Slayer, and Guardian Angel.
Kai’Sa, Shaco, and Fizz

Kai’Sa, Shaco, and Fizz are strongest when grouped in the old Spy Pilot composition. In this composition, Kai’Sa uses 3 damage-dealing items along with familiar effects: Archangel’s Staff, Morello’s Evil Tome, and Bombs. Additionally, Shaco with his pure damage items: Infinity Edge, Guardian Angel, and Death’s Dance. Whether in the old or new patch, Shaco is rarely picked as a carry in the Shadow composition, thus Shaco in this Spy composition will be the strongest version.
As for Fizz, this champion’s strength is mostly concentrated on Garen’s Shield, and if he reaches 3 stars, he can carry the team extremely well whether in Garen form or as his standalone entity.
Zed

In this composition, you will need to save gold and roll or hyper-roll (depending on the situation) to get Zed to 3 stars. The most important items are the Blade of the Ruined King and Guardian Angel for Zed; with this item combo, Zed just needs to activate the passive of Blade Master to also trigger his Weakness skill, leading to massive damage dealt and health drained.
Activations from Blade Master, Time Warp, Rebellion, or Spy all boost Zed’s power. Thus, this is the strongest playstyle for Zed at the moment.
Ekko

In the current 10.11 patch, Ekko is still quite powerful in the Cybernetic composition. Common items used for Ekko to carry the team effectively include Morello’s Evil Tome, Lightning Bow, and Sorcerer’s Hat (or Frozen Heart). With the right items and damage from Cybernetics, a 2-star Ekko’s skill can deal about 1/2 to 2/3 of the total health of the entire enemy team. This is the composition that maximizes Ekko’s potential in the current meta.

By patch 10.12, Ekko’s damage was significantly reduced (down to 100/200 at 1/2 stars). Additionally, the skill usage mechanism changed to target 5/7/20 at 1/2/3 stars, while the skill slows the attack speed of targets by 50% for 7 seconds. Thus, Ekko in the new Cybernetic composition has become a primarily effect-causing champion, while the damage-carrying role has been shifted to Vayne or Irelia.