This is a guide to assist with laying the ground work for playing jayce as an ADC, however this guide is geared towards a more advanced group of players. My reasoning for this is jayce does take some skill to play as an adc. Please read on and feel free to leave any feedback you wish. I do like when people critique my work.
As far as runes go I think most people use what they prefer on ADC but I find that i prefer to do more damage to players than creeps and I will get into that more later but this is the most efficient rune build possible while using armorpen/damage. again i will not be going into to much detail seeing as how most people will tend to use their favored runes. I will suggest however that if you play with more passive supports that cannot CC such as soraka or sona and you will be farming more than killing in your lane, stacking damage runes for quints and marks is never bad. The current rune build is kind of hard to last hit with in the beginning but you can make up for farm with kills in the lane.
On Masteries i use a slightly diffent setup compared to most other ADC the reasoning behind this is you have alot more abilities than just your ranged ones and when you switch you do not want your other abilities to get you killed by leaping into a 2v1 or 2v2 to solidify a kill.
When it comes to items with Jayce there are many ways this can be done and I will change my build based on how the game is progressing. I always start with boots and 3 pots, the main reason for this is because Jayce is a very slow hero and if i have some ground to cover to reach the target that my support is holding down for me it is the best item to start with. now depending on how your lane is doing this may change but in a good game i will retrun to base te first time and purchase a BF sword first because i always rush to the IE first. The IE is the cornerstone of the Jayce ADC build and here is why. Hypercharge is your main ability when playing as an ADC rather than just trying to poke with shock blast like most people do playing top lane(doing this will make your lane push by damaging creeps and getting you ganked) you will utilize the CC that your support has and pop Hyper Charge to get 3 instant attacks with a **** ton of bonus damage added. With on hit effects working on your Hyper Charge your IE will make short work of almost any hero in 3-4 hits and you can use the shock blast to clean up if they get away. the next 2 items are bought in the order that they are most needed. if you are in a game that has a very tanky team you will want the black cleaver first to help with armor pen to make sure you can continue to shut down any hero that comes in your lane. Now if you are already dominating and no one seems to be very tanky its a good idea to get the bloodthirster early and get those stacks maxed out. Also another thing that is great about Hypercharge is not only does IE proc on it but so does your cleaver and the life steal from the bloodthirster. you can get almost instant full life with 3 attacks from hypercharge and a fully stacked bloodthirster. after those items are complete if i have a good kill streak going to tend to build a GA next to keep my BT stacks and its good defense for when your targeted. the final item is your choice but i like getting atleast a sheen or a trinity force for even more damage on hyper charge.
The skill sequence is quite important when it comes to playing Jayce as an ADC. remember you are not solo top lane anymore so using shockblast to harrass is never a good idea because you can push your lane without even trying and get yourself ganked and thats never good. you will focus your targets with Hyper Charge and clean up with either the hammer or shockblast through a gate. this skill sequence never changes no matter the team comp.
Pros / Cons
The Pros for this build:
Tons of damage dealt very fast
once fed you dont need to be nearly as cautious as other ADC
You get to listen to people complain about Jayce not being a real ADC
Jayce has a short range
He is a slow moving hero
doesnt do well in a kill lane and requires a proper support lane
This is a vital part of this guide. Now when i play ranked with Jayce I am almost always duo qued with a blitz or taric support. My support will constantly start fights early game not nessicarily trying to get kills but mainly trying to win exchanges, bullying the other team out of farm range. I will continue to farm creeps and when a hook is landed i will focuse the other teams ADC unless the support is squishy or low. If i do target their support my support will exhause their ADC if needed to keep me from taking to much damage while we polish off a kill. These are just the basics i will soon post some videos of us laning together and can show you how we lane.
All in all this build is fun and tricky at the same time. It is very important that your support is on the same page. if you are playing normal games its a good idea to have 2 builds set up so you can lane with all possible supports.(more damage for a non CC support and armor pen for a CC support). Please Please critique this guide.