Athena, Goddess of Wisdom (Season 6)

Athena OP. Burst down squishies with your combo and really offensive passive that essentially has no synergy with the rest of her kit. Use hard CC to lock down tanks, and induce salt nuking everyone with your passive. Destroy in ranked or casual. Athena Support is really overrated, so play Jungle.

Pros:

Amazing Crowd Control
Global Presence with Ultimate, Defender of Olympus.
Amazing single and area damage
Great base protections
Reach deals extra damage with no movement penalty

Cons:

Dash and Ultimate require charge up
Entire combo interrupted by Beads
Easily locked down by Crowd Control
Requires moderate skill to use

Jungle Core

This item is actually quite powerful, although its passive activates in the midgame. It gives you very good Magical Power and then debuffs the enemy when using an ability, making all hits deal 10% more to them. Build after boots to get the passive as quickly as possible.
Shoes of the Magi: This item no longer has a Magical Power advantage against the Shoes of Focus, but it is still a very powerful item, as it has 10 Magical Penetration, which can shred most of any enemy's Protections early in the game. This could also be switched out with Shoes of Focus, for the extra CDR and Mana.
Polynomicon: This is the item that makes Athena's Reach Passive so powerful. It procs right after you use an ability, just like Reach does. It increases your next Basic Attack's scaling Power by 75% for the next 8 seconds, or until a Basic Attack is used. Since Reach is ranged and increases the next Basic Attack's scaling by 15%, 15% plus the 75% from Polynomicon and the 20% base Basic Attack damage, you will get a free ranged attack that deals 110% of your Magical Power. This item also allows for ranged poke and even finishing up opponents.

Solo Core

Shoes of the Magi: This item is recommended for the same reason that you would get it in the jungle.

Alternative: Shoes of Focus are also very good for a jungler, as they now have no Magic Power difference and, forcing you to choose between 250 mana and 10% cooldown or 10 pen. In S6, Focus is probably better, as Athena has long cooldowns.
Breastplate of Valor: A very powerful item that is quite cheap, the Breastplate of Valor offers ample Physical Protections, 300 Mana, 10MP5, and a whopping 20% CDR. This item is a must-have for anyone in the solo lane. Build this after boots if the enemy solo laner is a Physical god.
Void Stone: Another powerful defensive item, the Void Stone offers 60 Magical Protections, down from 70 in recent patches, but still very effective. It also gives you 150 Health, 20 Magical Power, and an interesting passive. The Void Stone is able to reduce the Magical Protections of all enemies by 20. This is a large amount, and is actually more penetration than any of the offensive flat penetration items. This item can really help in team fights. If your solo opponent is a Magical god, build this after boots.

Reach Reach is an amazing aggressive passive. After using an ability, the next basic attack instead shoots a spear that pierces all enemies, player deployables, and walls. It also deals an increased 15% of your Magical Power. This passive does not have any cooldown, so always basic attack after using an ability for added damage. This is best paired with Polynomicon.

Preemptive Strike This is your dash ability. It deals decent damage, provides a slow, and can give you up to three blocks based on the amount of damage that you deal. Level this second, but could also be leveled third if you prefer Confound duration. For high single target damage, level it first, although that is more of a casual troll build.

Confound This is Athena's main Crowd Control ability. It does not deal any damage, but can taunt all enemies for 1 second, plus 0.25 of a second per level. I usually level this third, but you could level it second if you value this more than Preemptive Strike. Very good when used with Shield Wall.

Shield Wall This is Athena's main source of damage and wave clear. This ability initially summons a group of Spartans in a circle, which deals a good amount of damage, who strike two seconds later, dealing more damage. When leveled to the max, it can deal 560 + 100% of your Magical Power, which is essentially the damage of an Ultimate when both hits connect. I usually level this up first for wave clear and damage. However, it relies Confound to deal the second hit. To maximize damage, use 3 and then use 2 just when the target walks out of the circle.

Defender of Olympus This is Athena's ability that allows global presence. It also deals massive damage when it hits. Level this whenever you can. This ability nukes enemies when playing in the jungler role with multiple offense items. However, if you are playing with random teammates, chances are that you probably won't be coordinating, which makes this ultimate harder to hit. You land at your current location if the target dies, so try not to use it on a teammate who is about to die. Best used on tankier solo laners or supports who get close to the enemies.

Your combos should go like this:

Shield Wall > Taunt > Basic in between each ability
You should always Shield Wall and then Taunt because Shield Wall has two hits. Taunting afterwards gives you the chance to make both hits connect, instead of just making one weaker hit connect. Using your basic will proc Athena's Passive, which deals an extra 15% of your Magical Power. This allows extra damage, plus Polynomicon.

Preemptive Strike/ Blink > Shield Wall > Taunt > Basic in between each ability
Preemptive Strike and Blink allow you to get up close to use Shield Wall.

Defender of Olympus > Shield Wall > Taunt > Preemptive Strike > Basic in between each ability
Defender of Olympus allows you to get up close, where you can then unleash your Shield Wall combo. Use Preemptive Strike to chase and use the Passive to snipe escaping enemies. Combined with Polynomicon, you can deal around 600 to 700 damage on squishies.

Currently a lot of better options for Jungle, but if you play Athena correctly and accurately, you can be a pretty devastating force. Other current S6 junglers would include Pele, Ao Kuang, and Ne Zha. However, Athena has some of the highest ban rates in the game, which means that you probably won't get to play her unless you are first pick and Athena is not first two bans, which is quite unlikely.

Use Taunt to save your allies. Note that opponents who miss out on kills due to Taunt will be extremely salty and may spam message you throughout the game. Taunt can also be used to gather enemies in one place for an ally to use an AOE ability, such as Scylla's I'm a Monster, Odin's Raven Call + Lunge, Hou Yi's Sunbreaker, etc.

Coordinate with your team to use Defender of Olympus. It has 20% damage mitigation, so use it on teammates who might be in trouble or teammates who are close to bunched up enemies. You can also combine your Ultimate with Ares's Ultimate to hit everybody, Ult to Hades when he is using his Ultimate, Baron Samedi, etc. However, coordinate with your team so you can set up your combos correctly.

In conclusion, Athena is a powerful Guardian with great offensive and defensive stats. She can be used in multiple roles and can succeed in every one of them. Combine different items for different effects to create devastating combos, and don't forget to use Reach. Polynomicon is a must. Coordinate with your team to make the most out of your abilities, and combine Defender of Olympus with other Ultimates to get Decide every time. Remember not to play Loki.