well, your gameplay is really unfluid because you dont use your abilities fast enough (sometimes not at all) and you also lack some basics of jayce.
use hyper charge before you enter hammer form. you pretty much miss the opportunity for ~7s (including gcd) to auto attack 3 times in a row for more damage output.
you misplace the gate many times, which causes you to run through the gate first instead of getting the movement speed buff instantly.
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thats too far away. drop your gate right in front of you.
try to avoid auto attacks as long as your hyper charge is down (jayce's AS is garbage). use your hammer form abilities instead if you are safe.
cast Q and then E first (cannon form).
general tips:
in some cases you should use your gate to kite first and then shock blast (e.g. versus riven)
dont build BC if you buy IE. get ghostblade instead.
hammer W has great base damage. dont forget to use it (first vladimir clip).
max q>w>e>r
cannon[Q>E>W>R] into hammer[Q>W>3x AA>E] is the standard combo.
watch other jayce montages/guides and see how they play. i can recommend this channel
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