You’ve finally decided to give up your SPA and move to a site that uses progressive enhancement, but you’re not sure where to start. Start with the server.
Instead of hitting the API directly, put a server between it and your site. Now you can start mapping remote calls to URLs that make sense for your particular site. Once you’ve decoupled your site’s URLs from the API’s, you can start transforming the content into different representations: HTML for initial page loads and JSON for AJAX requests, for example.