I used to build Oracle and take CoL in almost every Noble game,but now on Prince I do it rarely because I don't think it's worth it. If you don't have Mysticism you have to research 3 techs that you don't need early in the game.
Yes, this is the biggest issue. And it only gets worse at every higher difficulty.
For me to consider oracle, the map has to first say to me:
"
Dude, you need to go monarchy pretty early here!"
This makes the path through myst->med->pristhood not a wasted effort.
Basically the thing is that you can't really diverge too much from the teching that you really need, and the worker actions that you really need.
Some openings give you more freedom early on.
If you start with only one type of (early) food, such as only corn and you start with agriculture, or only seafood and you start with fishing or in the rare cases hunting, then you have more freedom with what to tech, and it's easier to fit in the oracle techs.
The availability of marble or not, is not something that I think too much about, the oracle is not expensive hammerwise so building it without marble is also ok.
Availability of forest is more imortant.
If you have marble riverside or coastal close to your capital, you can settle on the marble and get it connected right away, such that you don't have to tech the wheel or sailing to hook it up, you also save the large ammount of workerturns needed to build the quarry and road to it.