This is my first build so if there is anything that is done wrong feel free to say something.
To start things off Viktor is my favorite AP Hero. The reason I like him so much is this skills are unlike any other hero in the game. his Q help him win exchange and his W Provides a great slow fallowed my a stun. Hie E hits like a truck with range of a god. Final his ult with is under powered to eye but with is silence and damage over time has the poetical to get kill even when dead. Its like a super ignite with a silence.

Pros:

[*] He is never played or banned so there's that and a lot of people don't know his playing style or how much damage he relay can deal.

[*] His ult does tons of damage and can be redirected and fallow people to insure the kill

[*] He is Russian and half robot with a third arm. <- winner

[*] Hard leashes like a boss

Cons:

[*] If flash is not up you will have a hard time getting away from ganks

[*] He is rather squishy

[*] Hard to get play at first with is short range and his Laser being rather hard to direct

Viktor is a little mana so I get a little mana regen with the armorer because you cant kill if you died. the AP per level stacks nicely with his hex core. The magic pen is always nice to have on a AP so the MR does less.

Items are were everything comes together and a good build will make or break your lane. if your getting pushed out of lane and you are having problems with the other persons harass you should by 2 Doran ring not the blasting wand. If your dominating your lane and you can sustain your self you can some times jump to a needlessly large rod. if your against a AD don't be afraid to get the hour glass first. IF YOUR NOT GOING TO READ ANY OF THE THINGS I READ AT LEAST READ THIS when you get a new core your going to need to think about the role you will be playing late game. If your getting owned in team fight you might want to get a gravity core not the death core.

Viktor's farm should not be done with the laser until late game it will eat up his mana like crazy. You need to push when you creeps are low. if you use your Q push the other person out and protect you from minions that attack you.

Flash: it's a must have on viktor his escapes are not good even thought he has his gravity field if you get ganked we you best have your flash up. it is also good to pick up some kill just out of range of you lasser.

Ignite: if you use your ult and ignite them you are doing a booty load of damage. on top the the Death core's damage over 4 sec and you can look at someone with half hp and kill them no problem.

When your with your team you need to be in the back and lasering as fast as it comes up and hitting as many people as you can your slow needs to be planted right in the middle of the team fight with your ult. your ult needs to go out on the AP or support. if your fighting and your out numbered use your ult and the hourglass to do damage while siting in a nice gold form.