I took Ignite and Teleport for the simple reasons, Syndra loves to Tele Gank, and the purple just goes with Atlantean Syndra so well. And Ignite to help against people like Swain who without the ignite would be really hard to Duel mid game. Careful not to burn Tele after a recall or death to get back in Lane, it really should be used to Gank properly warded lanes

Ok, these looked so scary, now for your explanation.

I take the Flat and Scaling Armour to increase survivability mid-late game especially if they have a lot of AD on their team, same reason for the Magic Resist, Magic Penetration and Ability Power Marks allow you to do some solid early game damage which with Syndra's natural Poke doing tons already to squishy champs allows her to out poke almost anyone, the Quints should be obvious, CD Reduc to spam Poke and Ability Power for damage

Ok, these masteries are my standard AP masteries but instead of using the Biscuit (Cookie) Pots mastery I switched it and placed it onto the buff duration so that when you take Blue Buff it will last a bit longer, and if you and your lane opposition both get Blue (assuming his masteries don't use the Buff Duration) your Blue will last longer, same with red if you get a kill on a jungler with red. I put points into the offensive jungle masteries to help mitigate the fact that Syndra has really ****py last hitting (though eventually your Q will be able to clear entire waves in 1-2 shots, maybe even a squishy mini Gnar 1 shot)

Syndra doesn't really have any bad skins, but my personal favourite is Atlantean Syndra because of it's awesome spell effects and recall animation, and well, it just looks really cool. Justicar though is my least favourite because I don't like the gold colouring on Syndra, I like to keep it to purples and blues