You have Gotham why not use it through out (unless you only have one weight), I doubt a free font will be significantly better.
If it's because you only have one weight look at serif fonts to contrast against the sans serif.
Martin

Thanks Martin - I do have all the weights, just wanted to add a little variety. :)

I agree with Martin. Why mix it with another sans? There are condensed weights of Gotham if you’re thinking that Gotham is too wide for your headers.

If you’re looking for something ‘fancier’ you could also try Museo / Museo Slab, it’s ten a penny (actually, one weight is free – although I’d go with one of the extreme weights).

http://www.fontshop.com/fonts/downloads/exljbris/museo_slab_family_ot/

I'd really look at matching an opposing style to the body copy, sans on sans I've never really seen exectued totally successfully. You could always look at a slab serif, ie Archer by H+F the italic is really quite fantastic used in a headline.
Martin

I think a yoga schedule, even one that can afford Gotham, should be fine with a single family, using different weights for the text vs heads.

A yoga centre that can afford all the weights of Gotham.

And I thought all the wellness people are hanging out in isolation tanks these days…