The two strategies that really stand out for me in this vein are:
1. Take Mosques, Cathedrals and Pagodas. Take the reformation belief that gives +2 tourism for each of these. Spam them everywhere for +4 happiness per city and +6 tourism per city, as well as a ton of extra faith and culture.
2. Take the reformation belief that converts barbarians. Park a missionary next to every barbarian camp you can find. Enjoy your free unit fountains.