U are tooooooo brittle never leave people stay in them most times.

Never Ever go for mana pool it will ruin your game a lot the reason u are out of your mana is that your E Spends 60+ 15% max mana pool so if u have 5000 mana pool it will spend 810 mana that means u can use your E max 6 times but if u have mana pool of 800 u will spend 180 mana it can be look like u can press E 4 times but with around 20 mana regen per sec u are recovering that mana really hard so that's why we are focusing mana regen I litteraly draw graps for it and having mana flow is bad soooo bad.

in laning and most cases u can go out hiit and go in again your passive gives u mana and shield and while u are in people they will use that shield so in laning stage u can leave hit enemy and go back inside your adc u can take damage it's fine cos u are inside you will regain healt over time any way. Watch out for stuns if enemy have any stun wait for them to use that or dont risk it cos if your W get cd u are dead.

Yes u are brittle but still u have health pool u can go in front of jhin W so your carry can escape with u etc u can body block some skills just dont get stunned.