I tried using the God-King pantheon as Spain in two standard Emperor games with the following results:
1) Tradition, four cities, rushed shrine first every city
Result: scraped by, founding the absolute last religion, but had really awful choices for beliefs. I discovered the coast i was on was blocked off from the ocean by ice and thus had no real naval connection and restarted.
2) Progress, six cities, rushed shrine first every city
Result: Was beaten to founding a religion by the AI
I'm not sure what civs were in the second game, the two on my continent were Denmark and Germany. Neither game had ancient ruins turned on or religious CSs nearby.
At the risk of coming across as "I lost and therefore the game should be changed to accommodate me"...it seems kind of silly to me that Spain, a Civ with faith AND food bonuses, can't found consistently and definitely not easily with God-King, a pantheon that seems to me to be geared toward civs with early growth. I suppose from a balance perspective, the benefits scale over the game and thus a weak/risky start might be the trade-off, but if Spain can't consistently found a religion with this pantheon, there's no way in hell a non-religious civ would ever be able to. The faith output is just way too low. I really want to play Spain with this pantheon because it seems like it'd have great synergy, but it looks like building Stonehenge is the only way to make it happen consistently, which for a religious civ like Spain seems just plain silly.