I am buying an Athena groupset for my Bianchi Impulso build. Their 34/50 chainset is out of stock. Could I make a 36/52 work? I don't really understand the difference.

Groupset includes:

Bottom Bracket Options
Campagnolo Power Torque Bottom Bracket English
Campagnolo Chorus Cassette 12-27
Campagnolo Athena Rear Derailleur
Campagnolo Athena Front Derailleur
Campagnolo Athena Ergo Levers - ALLOY
Campagnolo Athena D Skeleton Brakeset
Campagnolo Chorus 11 Speed Chain

Campagnolo Athena Alloy Groupset 2015 - Black | Merlin Cycles

The difference is 2 more teeth, so not quite as low a gear as the 34. It's up to your legs to decide the best gearing. Everyone has different needs based on fitness, terrain, riding style etc ...

2 divided by 34 = .058 Round up to 6% difference between 34 and 36

I am going to assume you have some sort of road bike already, so should have a good idea of your gearing needs.

The 36/52 combination is known as a semi-compact. The racer does not sacrifice the sprint gear but retains lower gears by virtue of low ring substantially below 39.

That's a question that only you can answer. If you're more worried about climbing the upside of the hill, you should hold out for the 34/50. If speeding down the other side is your concern, the 36/52 will suit you well.

That make sense. Living in CA i'm more concerned climbing hills. So, i'll wait for the 34/50. I just realized my CAAD10 has a 34/50 as well so this is what i'm accustomed to.

Do the rest of my parts look kosher? I was confused which BB to go with. I'm assuming English is the standard.

If you can't wait, you could always choose a 12 - 29 cassette instead of the 12 - 27.

As for the bottom bracket, English threading is common, but you should make sure that your frame is not Italian threaded

I'm assuming 12-29 has easier gears?

Italian threaded..? How could I tell?

Sorry for noob questions - this is the first frame i build.

A 29 tooth large cog on a cassette gives you a lower low gear than a 27 tooth large cog
Italian bottom bracket threading has right hand threads on both sides. English threading is left hand on the drive side

Quick and dirty, measure the width of the bottom bracket shell. 68 mm = English, 70 mm = Italian.

Works moooooost of the time. My '88 Bianchi Premio has a 70mm English-threaded BB.