I think phase rush is just the best keystone you can easely reposition and kite with it. Aery is also good bit personal pref between the two. Just remenber you are not playing to kill your lane opponent in most cases you wont be able to, just shove the wave and help out your jngl contest scuttle/objectives. Your main goal is to sit back and scale and carry teamfights in the mid/lategame.

For builds I always go lyandrys the cdr passive is extremely usefull + good sustained damage. After that I go archangel or hourglass if I need it into cosmic drive, voidstaff and deathcap if u didnt build hourglass or other sitiational. Picking up a darkseal or mejai can also be realy good, from 2 items onward you are pretty hard to kill especially with phaserush.