I am not really good with the full guide but i like to share this build that i made and, i will try to give you as much tips that i know and possibly give.

i am gonna give you tips on how to handle your counters:

First off when you get yourZhonya's Hourglass, but when ever you face a Fizz and, when he reaches lvl 6 and, he hits you with his (R) Chum The Waters, Do you know that little 5 second timer, when ever his shark comes out of that little ring thing around you, right before that shark comes up like 1.5 seconds, thats when you wanna activate your Zhonya's Hourglass so his R can't stun like kinda thing to you and, it will remove the slow effects so that should buy you some time to flash or stun him hopefully both to get away from him and if you have enough health and some damage that you can still lay on him you could probably be able to kill him if not just run away.

So we got fizz out of the way, now to Kassadin just dodge or have someone go mid lane and you can try to support as syndra cause you will have no chance against a Kassadin
Because his combo is way to strong for syndra to handle or less you get Rylais Crystal Scepter then you might have a chance to take him 1 on 1 or less the kassadin sucks badly then your saved and you can go back to your lane or just stay bot support just to be safe.

K kassadin is aside, now to Diana
We all know she is tanky and, she is made to 1v1 other tanks like Malphite or rammus and, whatnot when you face her in mid lane try bring her to low health and, then try killing her thats how i beat every diana i play against.

Next is LeBlanc
she is hard to lane against cause of her Distortion and, her Sigil of Silence and, her Mimic abilities, but all you gotta do is try and stay out of her reach and, just farm until you get your Zhonya's Hourglass then you can try taking her on but if she get a Rabadons Deathcap then you need to get Rylais Crystal Scepter and your Zhonya's Hourglass cause she will nuke you hard if you don't got these 2 items, so you need them to hopefully survive like after you use your Zhonya's Hourglass you can stun her or flash away hopefully you can use both,and you need Athenes Unholy Grail for a bit of Magic Resist sooo yeah be careful against her she is hard to hit with your balls.

K thats all the counters that i have ever tried this build against the rest like annie and ryze and stuff like them is easy to face. I will update my build everytime i face another syndra counter.

now i am gonna give you the combo for syndra Q+Q+W+Q+R+E Dark Sphere and, then another then cast your Force of Will, on your first Dark Sphere then cast another Dark sphere then use your Unleashed Power, then use your Scatter The Weak, if it has the wide radius to stun the enemy or enemies to buy time or just to kill them or him or she either one xD lol.

The reason why i max my Dark Sphere and, my Scatter The Weak, is so i can farm way easier or if someone ganked you can stun them so you can get away, Beauce you hadn't gone back to get more wards after they were taken down by the enemy jungler or they just wore off or something like that.

hmmmm Well thats all i can think of, i'd say this is a gold build or silver build either one, if i have any Errors or stuff like that please let me know and, i will fix it please upvote :D or downvote D: !Thanks for trying it out or having a look at it! And if you want to know the scores on how good i am with her or too look how much damage or how long i spent dead or something like that look up my account on LoL 91DeathDealer91 because i don't know how to get pictures up on this thing and if you guys know how can you tell me how please??? i appreciate it thanks!