If I buy an unlocked iPhone 5s from apple store?

If I buy an unlocked iPhone 5s from apple store can I activate it with virgin mobile?

No, virgin mobile is a cdma carrier, you need a gsm carrier for an unlocked iPhone, Some of those gsm prepaid that have a prepaid price similar to virgin are:
Straight talk- unlimited everything $45 a month
Net10- unlimited $55
Metro pcs- 500mb 4g, unlimeted everything else (including 3g) $40

That should be up to Virgin.

One thing to note though, Apple likely will not sell the unlocked 5s in the US until at least November.

Doesn't Virgin mobile sell iPhones? Why not buy it from Virgin Mobile when it has it?