Here's what you need to know from what i've learned while playing her..
While warrior is better in the early game, devourer is better in the long game, play it based on how the game is looking
You need a pretty hard early leash, if you don't leave your first minion with half health your buff will murder your face hole.
It's hard to land a gank unless their closer to your side of the river unless the person your ganking has heavy CC
Yes, she's squishy, and yes, the patience fiddles with your kiting, but all you have to do is figure out that sweet spot before they start losing patience, and use your Q to just barely stay out of their range going left to right in an arc.
Your build is pretty basic, Jungle Item>BOTRK>Last Whisper>IE>Zephyr/Black cleaver(Just my choice, choose a damage item you like)>Then finish with a defensive or a situational of some kind.
Try your best to go for the enemy jungle camps for your passive, but make sure the enemy jungler is pre-occupied, or that yo know you can kill him.
Use your passive to select your next gank, OR, use it to play mind games, say your gonna gank bot? Set your passive to the Top Laner and make them think your going top! It's quite fun to see how people react, because that icon above their head is kinda scary lookin..
Last but not least, just play safe! Your squishy, so you need to use kiting to your advantage, don't go in by yourself unless you know their CC is down, or they will destroy you, use your E to your advantage to get a huge chunk of % Health off of them and use the slow to get ahead of them with your W Q Spam combo. Don't be sparing with your Ult either, don't save it for yourself, use it on your teammates, and try to win the 10% health trade after it runs out.