Maybe it's because I'm a lowly mobile user but there doesn't seem to be a way to find new circles other than browsing All. Maybe there can be a link that will bring you to a random circle to make it easier to find new communities?
On mobile, you can scroll to the bottom of the page to find a button for "View All Circles." This button is on the right sidebar on desktop (in All/New mode - not in individual circles).
On pc there is a link on the front page that will take you to a random circle, as well as one to view a list of all circles. I'm not sure how to find them on mobile but they do exist.
Currently, this page has a list of all current circles. But a random button would useful when Ovarit gets bigger!