It looks like flipping a civ to another religion is 600 base 
A spy with 50% bonus from waiting and 40% from our holy city + our religion present in a heathen's city, it will cost around 200 espionage to flip one of our neighbors to our religion (75-85% odds i think). We just need a lucky hindu spread, or gift a city that has hindu to one of our neighbors once our spy has sat in it a while. So there might be a reason to switch our espionage over to Tokugawa.
If they adopted our religion, we'd have +1 from years of peaceful relations and +1 from shared religion. We could gift a big tech or city and get +4, which should be enough for open borders (+6, if we didn't have border tensions ...) They would likely switch back to Buddism in around 5 turns and cancel open borders, so we'd have to send our missionaries and scouts through their lands right away. A religion flip is about the only way I can envision getting open borders with the Toku's in any kind of a reasonable timeframe.
We do have some options on what to Oracle.
1) Metal Casting is the most valuable tech, and it opens of triremes once we have sailing.
2) Code of Laws is rather strong, as it allows us to switch to Caste and run lots of scientists/artists/merchants in any city we wish.
3) Alphabet opens up exploring the map with spies. It also allows us to gift/trade techs with our terrible neighbors. One of my favorite techs to get early in Emperor games, but how useful is it with no tech brokering turned on?
4) Paper if we choose to bulb Theocracy and wait until T68-T70?
Madness.
5) Aesthetics. Opens up literature path and allows us to build that adopt-any-religious-civic wonder if we wanted it.

A spy with 50% bonus from waiting and 40% from our holy city + our religion present in a heathen's city, it will cost around 200 espionage to flip one of our neighbors to our religion (75-85% odds i think). We just need a lucky hindu spread, or gift a city that has hindu to one of our neighbors once our spy has sat in it a while. So there might be a reason to switch our espionage over to Tokugawa.
If they adopted our religion, we'd have +1 from years of peaceful relations and +1 from shared religion. We could gift a big tech or city and get +4, which should be enough for open borders (+6, if we didn't have border tensions ...) They would likely switch back to Buddism in around 5 turns and cancel open borders, so we'd have to send our missionaries and scouts through their lands right away. A religion flip is about the only way I can envision getting open borders with the Toku's in any kind of a reasonable timeframe.
We do have some options on what to Oracle.
1) Metal Casting is the most valuable tech, and it opens of triremes once we have sailing.
2) Code of Laws is rather strong, as it allows us to switch to Caste and run lots of scientists/artists/merchants in any city we wish.
3) Alphabet opens up exploring the map with spies. It also allows us to gift/trade techs with our terrible neighbors. One of my favorite techs to get early in Emperor games, but how useful is it with no tech brokering turned on?
4) Paper if we choose to bulb Theocracy and wait until T68-T70?

5) Aesthetics. Opens up literature path and allows us to build that adopt-any-religious-civic wonder if we wanted it.