Mid lane tower push

So I main mid lane, I play yasuo, katarina and syndra. I have m7 with yasuo and m6 with katarina and syndra. But I always find it hard to push towers as them or end a game. I find it much easier to push and end games with Diana and zed. With katarina your'e useless late game so you can't do that much syndra you have a decent team fight and yasuo your a beast, but my problem is I don't know when or how to take towers because, I'm always scared after killing my lane there jungle will gank. So does anyone have any tips on when to push when playing those 3.