Use your current MA to get as strong a background as you can in religious studies, philosophy, theology, or something of the like. If you can cross-register with other departments or other schools to beef up your studies in religion, then that would be good. I studied literature in undergrad then pivoted to religion. I have found it very easy to apply the skills I learned studying literature to the study of religion. Being really good at analyzing texts comes in handy! The problem is with background knowledge. There are a lot of facts, methods, and scholars that I had never learned about, and it felt like I had to catch up to my peers.
I found that reading scholarship about medieval religious texts has been very useful in learning how to bridge the gap. Scholars of medieval literature engage with the religious and theological context of the text, and often blend the study of religion with literary analysis. Also, it's interesting to read.