With syndra it is mostly about dodge ball.
If you want to hard engage, then someone who either can get in reliably (Sylas, Galio for examples) or someone who has fairly decent poke damage and some cc (Neeko, Zilean, Velkoz, Orianna) all in all it is mostly a skill match up.
An idea is to possibly invest in early boots to help dodge, and with champions like Leblanc try being a bit unpredictable. For example, dont take your W back right away, and sometimes you do. She will generally aim for your going back point on the first go, then if you stay then she will aim for where you are.
As for item matchups, banshees is good, Merc treads are nice, if Galio then Adaptive Helm is good, cho is good vs her too with adaptive helm etc.
Hope this helps.