Hi ! I'm solarus , I'm gold 1 at the TR server and I really enjoy playing the Millonaire playboy of the rift, Jayce,and think I play him decently well.I wished to write this guide due to some misconceptions jayce players have , so you can fast forward thtough these problems and smash faces.

Recommended Runes are:

Greater Mark of Attack Damage Greater Seal of Armor

Greater Glyph of Scaling Magic Resist Greater Quintessence of Attack Damage

The masteries are quite generic,Your everyday ad caster page, really. Double-Edged Sword gives higher damage , at the cost of taking more ,and as a champion who doesn't get close until it no longer matters to get damage, Its just earning free damage.
SorceryAllows Jayce to switch stances and cast abilites more often , which are his main damage sources.
Butcher Just simply makes last hitting easier.
Brute Force Gives a nice bit of much needed late game AD.
Martial Mastery Is every ad casters dream mastery.Free 4 AD.A must have.
Executioner Is an interesting one,I think it may and will allow one to deal that extra bit of damage at close fights, and Be more potent at diving low health targets.
Warlord Gives us more AD, The More AD we have.If you didn't get it yet,We love AD.
Dangerous Game Is another interesting one, though I think is a much earned point.This really shines at teamfights and first blood attempts.If you both have ticking over your head,you getting the kill first will help you survive.Encourages offensive playstyle.
Devastating Strikes Gives us much needed armor and magic PEN.Jayce deals a significant amount of both, So all good.
Havoc We came so far, might as well pick it up for the extra Damage. Block is great against autoattack poke , and really adds up.
Recovery is a nice little bit of sustain , also adds up in time.
Unyielding Also is an amazing trading tool ,Really matters through time ,especially in early game.
Veteran Scars Extra hearlth is just straight up good,And has synergy with the other defensive masteries we picked up.
Juggernaut Braum is here !Jokes aside ,nice little bit of hp ,If you have three thousand hp , you get 90 for free, nothing to laugh at just for a point.

When starting ,The Doran's Blade will be our pick as it now gives % lifesteal, and will be our lifesteal item until we finish our Essence Reaver , as it will help us to get the Pickaxe before the Vampiric Scepter.It also brings a good amount of health for duels.

After rushing Essence Reaver for Jayce's mana issues,We pick up our tier 2 boots for mobility.After our boots we grab our Last Whisper in order to go through armor and Grab our resistence item of choice which either could be A Banshee's Veil , or A Randuin's Omen. Randuin's Omen is still amazing post nerf and Jayce already has enough sticking power without it.If the enemy team has AP threats grab a Banshee's Veil instead.After go ahead And pick your Youmuu's Ghostblade for its active sticking power , After this Go ahead and pick up a Guardian Angel And you're good to go !

Jayce's passive Hextech Capacitor gives him 40 bonus movement speed and allows him to go through units whenever he uses his Ultimate , Mercury Cannon / Mercury Hammer

Quite a useful passive in name of going in for and out of trades,or just spamming to go around faster.

Jayce's Q ability, To The Skies! / Shock Blast is his main damage source in both stances.While in Cannon Form ,It blasts a aoe skillshot nuke dealing 60 / 115 / 170 / 225 / 280 (+1.2 per bonus attack damage) physical damage, which can be further enchanced by his E ability Thundering Blow / Acceleration Gate.

While in Hammer Form , Jayce leaps to his target ,dealing 20 / 65 / 110 / 155 / 200 (+1.0 per bonus attack damage) physical damage and slowing enemies by 30 / 35 / 40 / 45 / 50% for 2 seconds.Please note that although it is a point and click skill , it can be avoided with a flash , and Jayce will not follow.

His W , Lightning Field / Hyper Charge is unlike his other two non ultimate skills , is not a mechanically complex one.It is just there for pure damage.While in cannon form , Jaycegains a burst of energy, increasing his attack speed to maximum for 3 attacks. These attacks deal 70% / 85% / 100% / 115% / 130% damage.

This skill is amazing for persistent damage output , and following foe's,dealing massive damage in higher ranks.

While in Hammer Form, jayce passively gains (6 / 8 / 10 / 12 / 14) mana back by autoattacking ,and when activated he casts a electric aura dealing [100 / 170 / 240 / 310 / 380 (+ 100% AP)] magic damage over 4 seconds to nearby enemies.

It is notable that both instances of the skill persist through forms.

While in cannon form ,when cast deploys an Acceleration Gate for 4 seconds, increasing the movement speed of all allies who pass through it by (30% / 35% / 40% / 45% / 50%) for 3 seconds.The bonus fades away during the duration.If shockblast is fired through it ,It's damage is increased by %40.

While in Hammer form ,Deals magic damage equal to a percentage [8% / 11% / 14% / 17% / 20% (+100% Bonus AD)] of the target's maximum health, knocking the target back a short distance. This damage is capped against monsters at 200 / 300 / 400 / 500 / 600.

While in hammer form, Transforms the Mercury Hammer into the Mercury Cannon, gaining new abilities and ranged attacks.
The next attack in Cannon Stance reduces the enemy's armor and magic resist by 10% / 15% / 20% / 25% for 5 seconds.

While in Cannon form Transforms the Mercury Cannon into the Mercury Hammer, gaining new abilities and (5 / 15 / 25 / 35) bonus armor and magic resist. The next attack in Hammer Stance deals [20 / 60 / 100 / 140 (+40% AP)] additional magic damage.Feel free to spam it to travel faster.Try to get the oh hit effects as often as possible in lane to maximize your damage output.

These are where I recommend warding at ,I'll walk you through them.

Some extra knowledge to be had

Play Video

How to pull off a correct q e combo

Play Video

To be Added !

To Summarize , Jayce is an amazingly strong and fun champion to play , and one who definently has carry potential.

Feel free to leve any helpful feedback ,to report typo's,or say anything in general.English is not my mother tongue so If I made grammatical errors , feel free to be a Nazi about it.Have a wonderful day.

THANKS FOR READING

jhoijhoi for her guide making tips

To Ciderhelm For making amazing videos which helped me save a lot of time !
Link to his youtubez

Thanks to "Justin Gordon ",whose video I used to show a correct q e combo.
Link to HIS youtubez

to Metalocif for helping me with enlarging the build options [