Flash- Flash is useful for Jayce as he is already very fast and mobile. This spell allows him to get in range for that instant kill if he does not have time to wait for his R or ranged form E. This spell is useful for some of Jayce's skill combos and actually IS a part of some of his combos.

Ignite- This skill allows you to save yourself from some unnecessary risks by adding in a true damage DoT and a healing reduction debuff. This also gives you a nice set of AD quints (statwise) when it is on CD. Meaning if you make the plays early on you will be stronger while you wait to get it back.

Ghost- Ghost is a spell I have found to be a viable option on TANK JAYCE either anti-carry or protector. The mobility this skill gives you on the battlefield is amazing for getting around and doing all of your duties you need to do.

Heal- Heal is a very good spell choice on Defender Jayce. It allows you to act kind of supportish and heal your team as the fight begins. This spell has actually gotten more useful to take on top laners since bottom lane Doesn't take heal as often anymore.

Exhaust- I take this spell if I'm fighting a riven or champions to that regard who can burst you down in 1 combo, but after that combo if they didn't kill you, you get to penalize them. (IE: Riven blows her ult you exhaust, she uses all her CDs which deal reduced damage since she is exhausted.

Teleport- Teleport is an ok spell on jayce if you want to be a "Team Player". It gives you the ability to recall without missing CS, aid in dragon fights, and split push. The spell does however cost you kill potential in lane.