I like to create some new build for you so you can climb better from lower ranks. :)

LANING PHASE:
Dont be often agresive play more passively, just farm till you hit lvl 3 then go all in with support but let the support start the fight because you are such a squishy champion. I kinda prefer enemy to push you almost under tower so you can freeze the lane so you can farm more efficiently and if you have AP supp like zyra or lux they can zone enemy botlane and make your farming even more effective. When your oponent wants to last hit creep and they are low hp use AA+Q+W+AA+E(under them)+AA+AA then ult. If they are full hp and they want to last hit a creep just do easy combo Q+AA+W+AA and back off. You will take almost half of their hp.

Mid Game:
Be the one poking then from the back of your team, just poke, dont go full all in at the start because you dont have much mana so you will be useless after your all in, in any time you should take Blue and Red so you will do more true damage and have infinite mana. I personaly prefer to let my team go all in just shoot my W to hit someone and R from the bigger range so I can snipe them because you will get the kills thanks to the collector.

Late Game:
I prefer to go in mid lane between tanks and the assasins to I can do the major damage and try to get their adc because when their assasin will try to go and take me down my Tanks and assasins will take him out for me and I can snipe the rest of the team. Thats to the scorch and collector you will get most of the kill you will start because you will get the Scorch proc and that has big percantage to proc a collector at their low hp.

Thanks for reading this :) This took me like a hour to explain :) So I would like any comment what I could do better :) Thanks