Sure! What you want to do is avoid picking Syndra into her tough counters: Ekko, Zed, Talon, Yasuo.
For your first back, aim for 1,200 gold to get boots and Lost Chapter. Rush Morellonomicon because that is your best friend. Morellonomicon, Sorcerer's Shoes, Luden's Echo, Banshee's Veil, Zhonya's, Void Staff is usually what I build, but if I find that I'm really ahead, I replace Banshee's or Zhonya's with Rabadon's Deathcap depending on if I need armor or mr.
In lane when going for trades, only take trades when you have Thunderlords available and then back out after you activate it. Rinse and repeat!
In team fights, hang in the back with your team's ADC because if you are too close, Syndra's only disengage is her E which has a fairly long cooldown. Her ult always summons 3 balls. But you can make it summon up to 7 by having balls already summoned with Q. So make sure to have as many balls out on the ground before you ult for maximum damage.
Hope this helps! If you need any more help, just let me know <3