When playing Syndra, its important to set up before a fight, spam q a couple times to have one ready to pick up with w, and also to have more stun range if they walk within a path which you can stun them.

ask for blue buff, your q can drain mana quickly and its important u have have as many dark spheres up as possible.

Once you reach level 6 and plan to kill, use q in a direction you will plan to stun a target in, use it on minions to not make it obvious you are trying to stun them, press q again, and then use w to pick up the first q, once you have done that press e on the 2nd q and stun the target w q r should kill them without needing ignite.

at level 13 your damage will spike pretty good due to the bonus true damage it now gives, this with q and e can oneshot any squishy without needing ult,

around 4 items with rank 2 ult can oneshot most squishies

before an engage, spam q a couple times, dont do q into e for a stun, use w then e then q for a better chance of hitting your opponeny