Basically, everything but everything you do is wrong
Masteries shall be 23 0 7 or something, excluding the +4 AP and 1,5% damage, and going for Mana reg at utility
Spells 95% of times is Ignite and Flash. No time to explain, you cant just understand it for now
We first go for Q max, then E
about items depending gold.
Best time is to go for a phage only(1315) or both phage + dorans or boots. Going for double dorans vamp scepter sets u SO FAR BEHIND.
About your build. The standard route is Trinity + IE + last whisper or GA (depends on the armor they stack, which to build first)
Then finish the BT and thats all.
Only good thing about this is runes