Playing Jayce as a Top Lane tank has some significant advantages over a squishy Mid Lane build. Since Jayce has 6 abilities, you are consistently able to proc Sheen throughout a fight. This keeps your DPS quite high despite the tankiness of the build. Sunfire Cape combined with your Hammer form W can clear waves extremely fast as well as help you win extended trades. Your overall tankiness makes you extremely powerful in 1v1's because you still deal an insane amount of damage and enables you to easily survive 2v1's with your knockback and acceleration gate.

Jayce has very strong early game poke with E+Q in ranged form, just be conservative with your mana usage. His ranged mode also gives him easy harass against melee opponents. Overall you are quite strong early and if you can poke your opponent down to about half health you should be able to easily combo them down. However, this build really starts to excel during the mid game so focus on CS.

Once you have Iceborn your Mana problems should be solved and you can start to take towers fairly quickly. Keep your eyes on Bot Lane and Mid Lane for any TP plays. If your jungler is around, try to take Rift herald. Jayce's jungle camp clears are fairly quick so if you can take their T1 tower you should be able to do some counter jungling. Your armor enables to you tower dive fairly effectively, and the range of your E+Q can easily surprise enemies over jungle walls. Both E+Q will illuminate the Fog of War enabling you to swap to Hammer form and Q over the wall onto them if you are close enough.

Splitpush hard, turrets should dissapear to your Sheen procs and W in range mode. Your combined damage and tankiness will allow you to kill pretty much anyone 1v1 so look for picks. In teamfights, depending on your team composition, you will either be diving their Backline in hammer form to take out the ADC or be zoning for your ADC. Stay in ranged form pumping off Autoattacks and E+Q for as long as possible, once you swap to hammer in a teamfight you are fully committed. Keep in mind that for a short period after swapping to hammer you can run through units, attempt to knock their backline forward using your hammer if possible.