Asking for help with Vayne builds (Lengthy text)

It's been quite sometime since I've really played adc religiously; and with the patches from the beginning of the season changing everything and new items coming into meta (Such as ghostblade.); I've become a little lost. I myself prefer starting blade of the ruined king over Bt/I.E (so theres no issue as for a first item.) However; I myself am having a hard time choosing between Phantom Dancer; Stattik Shiv and Ghostblade! I understand the difference between the shiv and the Phantom Dancer; (I.E) you get shiv to trade better earlier on and give you a little more of a fighting chance, or you can get phantom dancer and aim for an even better late game; But ghostblade just throws me completely off. I understand why it may be good and how it can be used in synergy with her short range kit (being the 20% MS and 40% AS buff when active) but is it really worth it? I think its great that it gives some armor pen. and even a little CDR; but when the ghostblades active itself is on cooldown; isn't it a bit useless? Or do you guys believe that the armor pen it provides early delays the need for a Last whisperer so you can build one of the big swords earlier (I.E/BT/Merc. Scim). Any opinions on this would be much appreciated, I'm open to any advice anyone has to offer. Also; out of curiosity, Do you guys change your second item as a PD/Shiv/Ghostblade depending on the team comps/ situation at hand (Seeing as they're all used for relatively used for the same thing; When would you use ghost blade over PD or shiv?) Thanks again and I'm awfully sorry for the length of this post!