The trade journals like to stick stuff in your face ... like telling you that Gilt generates about 45% of sales via mobile (click here).
The inference - Gilt is smart, you are a moron.
Well, of course Gilt is smart. You don't go from $0 to infinity in a few years by being dumb.
But this doesn't mean that you are a moron.
You sell widgets. Do you have sale events that begin at a certain time and may have limited inventory?
Well, then there's not much in the way of urgency in your business, is there? Somebody can get your widgets anytime, anywhere. There's no danger of running out of widgets.
When there's urgency, then there's a need to use a mobile device.
So instead of thinking about "mobile first" - why not think about urgency? If you solve the urgency problem, you might just have a mobile business.
Oh, and Gilt, as you know, sells stuff at low, low prices. Low prices + urgency = mobile. You sell at high prices with discounts and no urgency. That's different.