I used Kulturista Web for my body copy but it depends on your design. I think Proxima Nova is a wonderfully designed typeface but it tends to remind me of old signage. I’m not sure I would use it for body copy. I’ve contacted Mark Simonson a while ago about a few issues it has at small sizes (Windows only).
Can you sign up for http://typecast.com and show us some examples of what you were thinking?
Here are a few choices that I would test out if it were my project.
And this is how I might style the headline: http://typecast.com/chrisburton/share/cbdc115852002fb2545ca9e6e239be9636ecfaadX7Nk7BtN
To be perfectly honest, this forum is targeted towards developers. You’re better off getting advice from those who specialize in this area. We can be found over at http://typophile.com.