The best build for each champion?

Quite often varies but:

turns you into by far the strongest duelist in the game finishes off the build.

is probably the best core dps wise

along with conqueror turns you into an unkillable monster that hrals for 700 every 3 seconds and deals insane damage.

This build makes you basically an AD Kassadin, you basically almost always have your spin up, and you get so much ad in your build that you basically 2-3 shot squishies.

Best build really depends on the situation.

Top assuming a balanced enemy team comp

- deep ward enemy jungle to avoid level 2 gank, bush behind red buff or bush on wall near river entrance by blue buff (I've had these wards last 30+ minutes before)

- insane mana sustian

- 151% cost efficiency

- preserve mana while farming ..........Swap these to bramble vest and thornmail if grievous wounds is needed

- Boosts damage a fair bit and finishes catalyst

Then whatever else you want from these

Finish last item

Against mostly AD (we make big smiley)

same start, whatever other armor item you feel like, it really doesn't matter because you are already a nightmare for your enemies with 400+ armor and heal for about 200 per second

Against mostly AP

same start, from here whatever you want. You have a fair bit of MR and now heal for about 700 on a 4 charge Q

Against an ADC top

same start, whatever else you feel is needed from previously listed items because you should just be able to auto win vs the ADC now with the slow from frozen mallet after landing one stun on them