Is 16GB really that measly when it comes to podcasts? Even at, say, 128MB per hour (!) you've got over 100 hours of capacity there. Enough for a full waking week, nonstop.
A single episode of a podcast may be an hour and a half. If you are subscribed to 5 weekly podcasts, then that's about 1GB of data you'll need. If you're going on a long trip, maybe you stock up. That might take 3GB or 4GB... But that probably won't fit on your phone. It certainly doesn't fit on mine.