Build late game with extra gold / highest critical hit you've seen

Hi, I am new the the boards...

But had a few general questions...for really late games, like when you have a lot of excess gold, what is best to buy. Literally the last game i played i had 3 ie, 1 phantom, 1 bloodthirster, and boots fully upgraded (sold my last whisp for more damage and 100% crit strike). What do you think the best late game build is (for adc/max damage).

Also, just our of curiosity, what is the highest critical hit you've seen/done with just item builds/no spells/enchants from other champions (i've had 1290?) on vayne which was legit!

Thanks for your feedback,

I appreciate it!