Jayce is a really cool champ but has little survivability and in early game his attack speed sucks. so this build focuses on those problems. When they first announced Jayce i said to myself i really dont want to just focus on one stance i wanted the ability to be able to change between them and not have much damage difference, so this build does focus on critical strike and attack speed, with AD and some survivability avalability.

These runes are made to add some survivability early game and up your damage throughout.
Greater Mark of Scaling Attack Damage and Greater Mark of Attack Damage give AD throughout the game and right at the beginning WHICH IS VERY IMPORTANT!!!
Greater Seal of Armor is great for armor which is a problem beginning game
Greater Glyph of Scaling Cooldown Reduction gives CDR which is always good.
Greater Quintessence of Scaling Magic Resist more armor!!!
Greater Quintessence of Scaling Attack Damage AD per level!!!!!!

Same as everything else, these masteries are set so that jayce does tons of damage but gives some survivability.

start with 2 Doran's Blades and Boots these are great items to start with because they give great stats and having 2 just ups the stats and they're cheep and you get rid of them later in the build.
then build to Ninja Tabi or Mercury's Treads, you could also get Beserker's Greaves, its a situational choice based on who your facing in lane or whatevers happening.
then sell 1 Doran's Blade and buy a Vampiric Scepter and after that start building to Trinity Force for all the stat boosts
Warmog's Armor provides a lot of survivability, but if you dont need survivability go straight for infinity edge and just throw in an extra Phantom Dancer or Black Cleaver at the end of your build.
Infinity Edge because crit is really good on jayce and is just super awesome.
Bloodthirster for awesomeness.
Phantom Dancer because its super awesome

only sequence that really makes sense, because Jayce's Q is a huge nuke. Then upgrade your W because in your Mercury Cannon phase it is really helpful for taking down turrets quickly. your E pairs well with your Q with mercury cannon and is a nice little stun/nuke with your hammer.

Ignite for damage. its a Damage over time thing which is kinda helpful as jayce.
Flash to get close with hammer and turret dive.
Exhaust is a good substitute for Flash if that's more your style.

Over all Jayce is a super cool champion with awesome spells and is good at solo top, mid, bot, or jungle.

Hey, please leave your comments this is my first guide and i want to know how i could make it better. also tell me what you think of this build and how it works for you.