Hello and welcome to my all around Jayce guide! In it I hope to establish enough information for you to play Jayce well and to utilize his skills to the max.

Pros: -High mobility -Not limited to melee -Crazy poke range -Can adapt to teams needs in case of trolls -Amazing burst -Counters many champs

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Cons: -If the enemy has a gap closer you loose your knock back as an escape. -Champs with high armor are a huge pain since all damage is physical (except mace form W).

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Top:AD carry:jungle:
I chose these runes, and all their similarity, because Jayce is 90% physical damage. This being the case it is a must to have armor penetration! The reason I take all armor pen when I am solo top is because you will end up against against tankier players, like Malphite and Olaf, and will need that little extra armor pen to take them down with.

On the flip side when you are an AD carry or Jungle you will usually be against squishier targets or the jungle mobs, which have very little armor. I still take armor pen because the enemy team might be tanky or their AD carry might have armor runes to try and out last you in early game fights.

Top/AD carry

The reason I choose to take boots and a couple health potions over Doran's Blade is because Jayce's ult is on a 6 second CD and his acceleration has a 10 second CD. So while you may have this wonderful boost of speed, one Exhaust and you are out of business, unless you wanna burn a flash (which might not even save you!). After that it depends on your style of play bruiser or AD carry

Bruiser

As a bruiser you will want to build tankier. This being said you will have to make the call of whether not you are dominating lane or not. If you are not dominating the lane you will want to rush a Phage for the health and movement slowing effect for escaping your enemies. After that you will build into Mercury's Treads then decisions come in to play.

Winning game/Tanky support or jungle:

When you are winning or your team has a tanky jungler or support you can build to deal more damage and be less tanky. I usually stick with my build but I will drop my Atma's Impaler and Warmog's Armor for either a Wit's End or a Madred's Bloodrazor and a Infinity Edge. With this build you will find that you can deal much more damage. Wit's End will give you more MR if you are against a fed AP carry or their team is just more magic damage.

Loosing game/Team needs a tank:

If you are in a loosing game you will want to stick with my build and maybe switch out a couple items for a guardians angel so that you can survive more intense fights. You really want a GA if you are the focus. If your team needs a tankier player go for dropping the triforce and trade it for something that will help you survive the onslaught of the enemy team. For instance if they are heavy AD you will want a Thornmail or if they are heavy AP you will want a Banshee's Veil.

Good summoner spells:

This is a very handy spell while laning Top or bottom. When a jungler comes to gank it gives you the ability to dodge skill shots and to avoid knock back into turrets (stupid Alistar). I usually take it while laning for that purpose, as well as late game it helps for wall hop ganks and escapes.
I take ignite while soloing top to help deal with annoying champions who have the pesky ability to heal themselves (examples: WW, Irelia, and Dr. Mundo) and so that if they are low enough for the ignite to kill I can hit them once and put ignite on them and RUUUNNNNN.
When faced with a champion like Singed who has amazing movement speed boosts it is very helpful to slow them down a bit with a nice exhaust. I take this while jungling because it helps ganks go more smoothly because they have reduced reduced armor with masteries.
Ghost is ok but with the passive bonus to speed while switching weapons and his acceleration he really has no need for ghost.
Smite is a must while jungling because Jayce will struggle in the jungle with out it and against a Shyvana who invades a lot it will be a huge problem. It also helps secure Baron and Dragon.
I take this when I am AD carrying because it is good survivability while laning bottom.

Alternatives:

A good alternative to heal while laning bottom because it helps escape Taric's stuns and other CCs. I do not use it because WW's ult and Malzahar's ult are not effected by it, same with Malphite and any other knock ups.
This is terrible when in the jungle and AD carrying. But while top it can help you return to lane quick and to gank other lanes or tele to a ward in the jungle for a kill.

DO NOT TAKE:

For all of these JUST DO NOT DO IT!!!!!!!!!!

AD carry:

For skill sequence you might be wondering why I max out his W first rather than his Q. I chose to level up this way because it is very helpful for ranged carries to have high burst damage when they engage fights. If you notice W starts at only 70% damage for 3 shots, this is not very good. At rank 5 it is hitting for 135% for 3 hits. This can eat away at turrets and enemy health bars like no other. Where as his Q is good poke and has the nice hammer drop, it really doesn't make him an amazing AD carry. Obviously you could level it up to rank 3 and then max Q so that W hits for 100% and still have amazing poke from Q.

To be honest this all depends on your own play style. If you like to be aggressive and poke them a lot, max Q. If you like to wait for the jungler for a fight, max W so you can bring them down quick with burst.

Solo top:

I max Q first for a solid slow and good burst damage while in mace for as well as the harassment you can dish out with it in cannon form. After Q i like to max E because it has a % damage to the targets health, this means you can take a big chunk of their health out in one swing. I take one point in W early for the rapid fire when pushing a turret and the electric field for clearing minions quickly.

Jungling:

As jungle I take a mix of all of his abilities maxing Q first for its nice AoE damage as well as the acceleration and Q combo starting groups at half while jungling. I usually mix and match W and E for a quick jungle with strong ganks. What I mean is that I get 2 points in W early so that I can move through jungle quickly and gank very often.

While farming as Jayce you will find it much easier to farm with cannon mode because it gives you a nice comfy range from which you can harass enemies who try and farm, as well as killing minions without getting too close. As you should with all laning LAST HIT I can not stress this enough. If you do not know what that is look it up on Youtube or Google it. If you are out leveled or the jungler is babysitting your lane the alternative to farm is buying a Heart of Gold to help you keep up with your opponent.

While farming if a large minion wave starts to form you can use an acceleration and Q combo to kill them all off quickly and efficiently and stay REALLY farm away if you are low health. Just don't miss!