Since the winter update, my challenge has been a deity, marathon, huge map as Poland, going for religious start and cultural finish. I have not succeeded yet, out of over 20 starts. I was only able to found a religion twice. Both times I built 2 slingers then holy site in capital, setting it to holy prayer project after that. My army in its first war was able to capture a settler then the npc negotiated peace with a gold sum I turned into a shrine in my capital. 2nd city made an extra slinger or archer, then began the 2nd war, conquering a npc city that already had a holy site + shrine going. My pantheon was Divine spark and I still had to faith buy the prophet, one time getting the 2nd religion and one time the 3rd.
In my best attempt, I war-mongered my way to Gunpowder only to discover that to acquire niter, another military campaign was needed, but a Mamluk defeated my army. After a few more failed restarts I'll probably go back to that game and attempt to hold peace, or maybe the winged hussars could change the tide, haven't gotten to those yet either.