AD build: Jayce Is incredible with his abilities, most champions can do 4 abilities and that's it, But Jayce Can do 6, Every ability has it's part in doing damage even his Transforming ulti can boost your damage, So imagine 300AD with a Sheen .

Off-Tank: I guess you cant really call it 'Off-Tank' since he is not a tank, and doesn't have much CC on him, So let's just call it a 'solo-top' build, It starts with a sheen to maximize your harras damage, and then it goes to a mid-game build.

AD BUILD:

Greater Mark of Desolation Greater Quintessence of Desolation: You need to do damage, that's how Jayce is played, And since you won't have armor penetration items until late game, this will do for now.


Other possible marks or quintessence:

Greater Quintessence of Attack Damage Greater Mark of Attack Damage: Pure AD is good for you and your harras early game, also you need those big damage outputs to your enemy, and this AD goes straight to your abilities' damage.

greater Seal of Vitality: You need this for durability, and there is no other seal that I can think of that helps Jayce, also there is a big chance of the enemy team being mostly AD, or to share the lane with another AD carry.

: Jayce + Attack speed = Tons of damage, all the attack speed you get will help you do more damage of-course but.. it will also help your Lightning Field / Hyper Charge passive to gain mana faster, and clear minions faster.


Other Possible Glyphs:

: Those help your durability, how to pick between them is dependent on you and which you feel helps you more.

AD BUILD:

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Every time you transform from range to melee or melee to range you will gain extra movement speed and ignore unit collision, a useful way to get back to your lane, just keep spamming that R and Acceleration Gate and you will be there with no time.
also useful for catching running enemies.


To the skies (melee):
People forget that this slows enemies, Well I just told you so don't forget it in-game, this is your gap closer and it's better than most others since it will slow the target.
this also deals damage to nearby enemies making it a great jungling weapon and a perfect ability for farming/pushing.'


Shock Blast (Range):
This became my favorite harras ability! this is just awesome, Deals damage to your target and nearby enemies, if it doesn't hit anything it still explodes dealing damage to nearby opponents. This should be on cooldown most of the time, it has a nice cooldown and mana cost, so use this when you can even if you have to use it on the minions (if they are grouped up)
When using it with Acceleration Gate it will gain a bigger range, faster pace and the damage will increase, making it the perfect boost. Just make sure you take an angle that you can use this technique to hit champions without it hitting minions.
ALSO DON'T FORGET! you can reveal the 'fog of war' with this ability, so using it in the brush can help you detect enemies there.


lightning field (melee):
The passive gives you mana every time you strike in melee form, so if you think you can farm with the melee form without dying or taking serious damage do it.
to maximize this passive, when minions are close to tower make sure you hit them with melee, since the enemy champion(s) will be back for safety.
You can activate this ability before you're near the enemy and it will still deal damage to them, so you along side farming this ability can be used to harras, Activate Lightning Field then jump with your To The Skies! do a basic attack then Thundering Blow and go back to safety.


Hyper Charge (range):
if you have low hp use this ability to hit minions and gain a little hp from your lifesteal, this also helps jungling but not that much, you should use this ability when someone over-extends, you activate this ability, hit him 3 times then Acceleration Gate and Shock Blast combo.
people don't use this very often: This ability has a good lasting time, so you can trigger it then transform to your melee form and gaining more damage since now you can use 4 abilities.
if you are lanning against another Jayce go to the brush then use this on him, it will make him run with a big hp difference between you two.


Thundering Blow (melee):
This is a good last blow, it knocks back and deals damage based on their health, making it a good way to start and end a fight.
if you are chasing down an enemy and want to hit him with Thundering Blow then take an angle to the side a little and use it on him, this will make him knock back to the side more than you think.
also a way to stop an enemy (only 1) from chasing you, using it then gaining speed by transforming and Acceleration Gate will pay.


Acceleration Gate (range):
Boosts your and your team's movement speed, doesn't have a big mana cost so use it while getting from your base back to the lane.
use it on front your CC dealing teammate when chasing down enemies.
Always use it to harras with Shock Blast.
ALSO DON'T FORGET! you can reveal the 'fog of war' with this ability, so using it in the brush can help you detect enemies there.


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your first hit since transforming will reduce target's armor and magic resist, so if you are able to use it on a champion do so, then try hitting your Shock Blast.
this stance/form should be used for farming from a safe distance or harrasing.


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your first hit deals bonus damage, transforming to melee then hitting a To The Skies! then a basic attack will do a big amount of damage early game, so make sure you do that.
you should use this stance/form while jungling and if you are able to farm safely to gain mana from Lightning Field / Hyper Charge's passive.

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good for Jayce to insure the kill, and stop those enemies that feed on lifesteal like Dr. Mundo, also activating Ignite then a Shock Blast combo would be enough to get the kill.

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A must have for a carry, A gap close and a good getaway spell, and don't forget flashing over the walls to chase or escape.

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Only if you're a jungler.

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If you rather play safe, replace Ignite with Heal.

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Also a possible one for Jayce but I think that your Acceleration Gate and ulti can boost your movement speed enough.

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Not bad if you're top or jungle, but if you're bot leave it to your support, top or jungler.

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only if you're top, but I don't think it's needed for Jayce you can get back to lane faster than tanks, so there is no need for this.

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Never saw it used good, and you have your Hyper Charge it might last for a while but it doesn't have Surge's cooldown.

Your main objective early game is to gain as much minion kills and harras, get only last hits and don't push your lane, if you push your lane keep an eye on the river ward and stay in the brush, you can be easily killed if caught off-guard.
Of course harras by putting an Acceleration Gate then a Shock Blast through it, you don't even have to hit the champion himself sometimes, if hes hiding behind his minions and gets too close to them, simply hitting the minions will also damage him.
Don't go aggressive and start a balanced fight between you and any other champion, because Jayce is not that good early game, just make sure you are getting those minion kills.
Players usually forget and push their lane, so let them push and make that mistake then play a gank with your jungler for firstblood.
if you are un-able to farm go in the brush and start harrsing with your Shock Blast.
When the enemy team's minions get too close to your turret or you feel that you can farm in melee form safely then do it, Don't forget Lightning Field / Hyper Charge's passive, so get as many hits in melee form as you can.
By your first recall you should at-least get 2 doran's blade if you are doing good, or finish off Berserker's Greaves, also it's optional to get Sheen.
By your second recall if you are able to get b.f. sword then get it.


It's time to gank and counter jungle, by now you should be farmed well enough to have a good amount of AD in you, when your lane is pushed to their turret you can go mid and gank, or counter jungle by taking the wolves/golems (Depends on your side), Just make sure when you counter jungle that their jungler is no where near you.
When you gank prepare Mercury Cannon form, if you are already in that form, change it to Mercury Hammer then back to the cannon for it's bonus, stay in the brush and make sure he doesn't see you, if it's warded then try taking an other route or approach, when you are ready put a Acceleration Gate and fling a Shock Blast through it and hit him with your basic attack if you can, then you can trigger Hyper Charge and change to Mercury Hammer and use To The Skies! on your target, place that gate earlier will give you a movement speed boost enough to catch your target, if your teammate deals enough CC your target should be dead by now, if not you can use your abilities freely, remember that when he runs away place a Acceleration Gate fling a Shock Blast and go through it to catch him.
Bottom line here is to gank as much as possible, and still get a good farm.
By the end of this phase you should have Bloodthirster and a Zeal.


The most important thing here is team work.
Get dragon and baron as soon as they are up, placing a ward there would help, also take the buffs as soon as their up or help a teammate get it.
make sure you push all lanes carefully, if the enemy team goes MIA or SS back away and gather with your team.
In team-fights let your tank go first, since you are the carry stay back and wait till your team initiate then join the fight, as first as you join do the Acceleration Gate and Shock Blast combo, then with your Hyper Charge auto attack the hell out of them, don't do something crazy and dive in between them in melee form, you will be destroyed, you only use your melee form in team fights when:
1- They get separated:
Meaning they stop focusing one guy and start getting confused and scared or some of them back off or runs away, when you there are only 3 left fighting of them, whether the others died or ran away, you may use your form but remember just cause they ran away doesn't mean they can't pull a clutch and kill you.
2- Someone over extends at you:
Like I told you, you should be back not engaging in a close distance, so when someone focus you alone you should switch to melee form gaining bonus defense stats, also activate Lightning Field and hit him with Thundering Blow.
3- most of them die and 3 or less remain:
If this happens with most of your team alive or you have most of your hp, then you can charge melee style, spamming those abilities. When they start running put a Acceleration Gate to boost your team's speed and catch the rat.

In this phase if you feel that you are not protected by your team, or dying very fast you should consider getting a Frozen Mallet or zeke's herald or just get Trinity Force before Black Cleaver.