After you pick up your Rageblade from that warped little goblin bastard in the shop you are going to need attack speed to help get stacks on the blade. Since your W gives you additional movement speed and Kayle is not reliant of landing crits in order to do massive damage, zeal is fairly useless. People that I see go Trinity Force Kayle really rustle my jimmies. if you notice the other team is giving you funny looks you should get Wits End because it reduces magic resist and is plain freakin awesome, but if you see that the other team isn't really applying that much pressure on you and focusing other members, then Ionic Spark will really help your damage input in team fights. HOWEVER, since Kayle's passive already reduces magic resist you should only get Wits End if you notice the other team picking up MR (magic resist).