I always rush BT first out of habit on my ADC, no exceptions. However I see a lot of people rush IE first.

I understand this is a situational thing - when do you rush IE first instead of BT? With which supports is it advisable to rush IE instead of BT? Are there any carries for which it is essential to rush IE first?

Thanks.

depends on the champion. if they have a lot of moves that scale with ad i build BT first. cait or graves for example.

for IE first, i rush it on champs that depend on AA for damage liek ashe and kog maw.

I always get IE first, but I make sure to take AS through Zeal or something. AS is particularly important on the ADCs with CC, like Ashe or TF. BF is for an additional lane sustain, but why get it? By the time you do, the laming phase is closing, and your DPS now matters more than sustain. Maybe if you are Caitlyn versus a poke comp or kill lane, but IE's passive is crucial to that DPS.

Oh, and I love going double Phantom Dancers. 100% critical hits crate the same DPS as BF, and with IE and attack speed, it beats BF.

IE does way more right click damage... You get IE first on champions that can get away with building glass cannon. Usually build IE on champs like ashe and tristana, because they have huge range and kite ability. On heroes like varus and graves, who both have AD abilities with good scaling, you build bloodthirster. These heroes tend to have more of a bruiser mentality, I need to stand and fight type champions. Ashe and tristana tend to die if you pinch them.

Another thing, When you build blood thirster your intention usually is to keep farming, if you get IE you can teamfight really well, and often it's a good idea to just group up and push..

It depends on whether you need the sustain to stay in lane or to win trades/fights early on. If you're winning the lane handily you may want to skip BT and go straight to the IE for higher damage output. If you're behind or the lane is even, a BT may be a better pick. There is no definitive answer.

I now prefer to build Bloodthirster first because of the extra sustain from Vamp Scepter.

IE first for people like kogmaw who rely on autoattacks. But sometimes you'll want to get zeal and lifesteal first. On people like vayne who are squishy or ezreal with his on hit effect Q the sustain from bloodthirster helps a lot. It just depends on how much u end up autoattacking with a certain champion early game.

Just a quick note: On Draven you DEFINEATLY want BT first.

Bloodthirster as a first item came into popularity among the pros near the second half of season two because any team with the slightest zoning skill will keep you out of a teamfight unless you have some sort of sustain.
Now that it costs twice as much to buy a vamp scepter on the side, BT is almost a mandatory first pick on carries.
I know, it's fun to be dealing as much damage as possible, but that damage won't be doing you any good if you have to run out of a teamfight halfway through.
Go ahead and check lolking for players with the highest winrates on carries- 90% of them start Bloodthirster.
The possible exceptions to this rule are Tristana, Ashe, and Caitlyn, but even that depends on our team's comp.