Well this is my first guide ever, and as i know Quinn, just released so it will be hard to determine, which items is the best. I have been playing with her to get some results, and this is what i prefer to do, you could switch some items out or change the masteries a bit.

Marks

There is a 2 options here, either use attack damage, to get some damage on both champs and minions, or go with armor pen for great damage on champs.

Seals

Here there is not really an option, you need these runes to survive and not get roflstomped.

Glyhs

Here i prefer Cooldown reduction, but if you want to survive AP carries choose MR runes instead.

This is pretty much it so far, i will add more to the guide later this week as i need to play her some more. I will add mastery/Item chapters, and some pros/cons. I will probaly change the items as well but for now this is my guide.