Not Updated For Current Season
First start with a vampiric scepter because it gives u a lot of survavility and help u stay lannin for long time, with this u will be able to farm enougth to get chalice of harmony and then some booots (berserker graves would be fine).
After that you will notice that u dont have atack, so get sword of the occult and then start stackin, sivir is pretty goood gankin so it wont be a problem.
After that get phantom dancer for atackspeed/crit, and finally end with more damage, infnity edge or blooodthirster would be good.
Why u want so much atack?? because the atack also makes ur Q ability to hit harded, so u will ace the whole team with 3 Q´s.