Power Greninja 2.0 Greninja - PokeGamerBoy17

Guide

This is a high-skill damage-dealing build that best uses Greninja's natural healing ability to stay in battle longer.

Before I start, I need to explain a couple things.
First, the basic attack is special because it has both a melee and a ranged attack. When ranged, it reduces the cooldown of Bubble or Water Shuriken (or Surf if you're playing that build) by 0.5 seconds and boosted attacks reduce enemy movement speed by 25% for 0.5 seconds. When melee, it deals bonus damage equal to 5% missing HP (calculated as basic attack damage and subject to basic attack effects). Boosted melee attacks also dash through the primary target and increases the missing HP damage to 10%. The melee attack also deals damage in a small area of effect.
Next, Greninja's healing mechanic allows it to heal with every basic attack it uses. With a Lifesteal stat of 15% (level 13+), you heal 15% of any basic attack damage you deal, no matter what. When combined with all 3 held items this build uses, that can be a good chunk of healing.

Now, onto the build guide.

Start with Substitute and go towards the central area. You can just barely roll through the wall with Substitute when timed correctly.
Alternatively, you can start with Bubble and take either of the other two lanes. Any option is viable.

Once you have some Aeos Energy, try to start scoring goals so to max out the Attack Weight as soon as possible.

Double Team has a special mechanic where, when used, the clones will attack for you. They have the same stats as you, but they take 500% damage and deal 18% damage. However, this is still very good if your Attack Weight is high. The clones will automatically target the nearest opponent or wild Pokémon and attack with Bubble or Water Shuriken. They will disappear after 3 seconds, though, so be careful when you use it.

Once you get Water Shuriken, the real fun begins. You can start dealing massive damage quickly and stay alive if you played the early game right. This is also where your held items will come into play the most.

Scope Lens adds onto Greninja's base crit-rate of 30% (level 9+), which can make for some deadly, half-health-killing single basic attacks. (Yes, I've done this and it's insane.)

Rapid-Fire Scarf just adds onto literally everything Greninja is good at. If you're not using Rapid-Fire Scarf on Greninja, you'd better have a really good reason. This item simply boosts basic attack speed for a short time after three basic attacks. Greninja lives basic attacks. Combining Greninja's dual basic attack mechanic, its high Lifesteal stat, and the Attack Weight and Scope Lens, Rapid-Fire Scarf is just too broken not to use.

X Attack can actually come in clutch in many situations, especially since Greninja heals based on how much damage it deals. When Attack goes up, healing goes up. Use this in tight spots to get out alive. And no, Double Team clones don't get it.

The best distribution of brown and red boost emblems is shown below. (Ho-Oh is brown in game)