IntroductionJayce is very good AD champion.Changing between those two stance that he has is the key of victory.
RunesFor runes i recommend crit chance runes.You will do plenty of damage on first level if you buy him Brawler's Glooves.
Passive: Hextech Capacitor
Q: To the Skies! / Shock Blast
W: Lightning Field / Hyper Charge
E: Thundering Blow / Acceleration Gate
R: Transform: Mercury Cannon / Transform: Mercury Hammer
Skill OrderFor the skills i recommend to grab his q,then his e and then his w.
Item BuildsI recommend Nashor Tooth because Jayce's hammer's W is the only skill of Jayce that is using Ability Power,but you can play it Full AD.
MasteriesThe same for like the build.Get some ability for the W.