how to build full ad poke varus?

i saw a friend do it and its pretty fun. this varus focuses on cdr and ad to spam his q. since he has a lot of AD he can also autoattack but he shouldnt because he buys no attackspeed at all. im just leveling a smurf right now and i dont have a lot of champs so i usually pick him mid, or when i play aram i sometimes get him.

but i have problems with building him so if ppl can give me some help that would be great. first item is tear. it just really helps out a lot with the mana problems he has from spamming q. i finish muramana as 4th item (is that too late?) i tend to get as 1. completed item. the active gives him speed and attackspeed + you get cdr and armorpen and a decent amount of ad from it. between 1. and 2. item usually (since im midlane) i get as 2nd item. MR and more armor pen 3rd item usually is . more cdr and lifesteal on the q which really hurts by now. 4th item is or 5th item is or (40% cdr at this point. or 45% with masteries but i dont like them much) i never got to 6 items but i'd get as 6th.

is this a good build? i cant tell should i get IE + Reaver for the crits and cdr? but why should i get much crit when i spam q (and ult) instead of aa. or should i bet a BT somewhere?

pls help me guys :D