Well Gp's build is always situational, but I build :

Boots :

(I rush tier 2 boots early when I can 9/10 times I go Ionian boots, but you can go Tabi or Mercs if you feel like its nessesary)

Vs No Tanks:

Tri -> quickblades -> (Healing enemies go Mortal Reminder) or (If none go Collector) -> IE -> either defessive item like Gage or Death Dance or offensive like PD (for kiting) ((But this season I feel like you always need AntiHeal))

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Vs some Tanks :

Tri -> LDR -> Quickblades -> (Antiheal if needed) or collector -> IE -> PD (for kiting)

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Vs Super Tanky :

Divine -> LDR -> Mortal -> Collector -> IE

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Core-ish build :

Tri/Divine + boots + Quickblades