These are the only runes I would use on Jayce, it is up to personal preference on which you would use, I recommend always brining armor seals however as they will help a lot in the top lane

You can spam your R when running to lane to get there quicker because you get it at level 1, costs no mana and gives you a speed boost.

Jayce has amazing wave clear after he gets his manamune with his cannon form E and Q.

Last hitting is the key to early game success, it is much easier to farm when in cannon form so unless going in for the kill you should be staying in cannon form.

Don't forget to clear any wards your enemies may place with the scanning trinket so you can ask your jungler for ganks

Never level up your ultimate unless forced to because it gives no improvements.

Jayce is very mana hungry at early levels so don't spam his spells until you can get your tear stacking.

A neat combo you can pull off if someone is at your turret in hammer form is Q, get behind them and then E them to the turret.

Jayces early game is very strong so try to take advantage of it.

Jayce is one of the few Top laners with ranged attacks so try to poke your opponent out of lane if possible.

Most of all have fun!

Riven Easy Simply abuse your range and don't let her get too close.
Renekton Medium Renekton has a lot of sustain that Jayce does not however unless he manages to get in your face you will stomp him.

If you want me to add any more match ups just ask however against most melee bruisers as long as you don't get too close its an easy win. Jayce is a very safe pick.