Jayce is a great champion if used properly. If not used fully, he will be weak and not very beneficial to his team. However if his abilities are used in the greatest way, he can prove to be a great carry, inflicting great amounts of damage while also setting up kills for his team.

Pros
> Great Laner
> One of the best ganks in the game
> A lot of damage if abilities used well
> Can set up kills
> Great AOE speed boost

Cons
> low early game damage
> Squishy early
> Slow clearing time early
> Gets low in jungle

Jayce can be built as a cc/tank, a beefy bruiser or a glass cannon carry. If your wanting more damage i suggest replacing the GA with a PD.

So why does he have one of the best ganks? Because they consist of a lot of damage, great cc and an aoe speed boost.
When ganking, use your abilities in this order:
Start in Ranged mode and place down your E, if you can place it in front of your allies. Use your q to initiate with great damage and then Switch to your hammer. Start your W then use your Q to land on the fleeing champion. E the champion back towards your team and this should be an easy kill. If not, switch back to your ranged and W them and IF its really necessary q them once more. If this is not a kill, then the lane obviously didnt help u at all.

When Laning you should stay in ranged form and only switch when your jungler ganks or your initiating a 1v1 fight. When fighting a 1v1 or if your jungler is ganking, you should use the same order as above. This will give good damage while also making time for more damage.

Do NOT INITIATE. As long as your not initiating, you should be focusing the carries, either the ad or ap.

When clearing, be sure to switch your weapons a lot. I like to start ranged and use my E-Q combo then w, switch, Q-W-E. When he gets his full combo he clears well. However at the beginning hes kind of slow, and takes a lot of damage.