To work up the religious education career track, I would propose from lowest to highest
1. Student
2. Novice
3. Acolyte
4. Deacon
5. Priest
6. Canon
7. Bishop
8. Arch-Bishop
9. Cardinal
10. Pope
Not everyone can of course progress even to level 5 (basic character statistic requirements, e.g., diplomacy 8 to become bishop?). Level 6 and above would be appointed positions. Level 4 and above require promises of celibacy, at least in the West. Level 3 would represent "minor orders" that do not require celibacy, at which point the ecclesiastic can break off the track, following a career in royal service (which of course deacons and above can do as well).
For females,
1. Student
2. Novice
3. Nun
4. Abbess
The ecclesiastical track has some departure points, especially for men. If regular orders like Franciscans, Augustinians, or Dominicans exist in your realm, Students can enter these orders as Novice, progressing from there to Friar, then Abbott.
Entering military orders (e.g., Knights Templar, Knights of Santiago, Teutonic Knights) should be possible either from military or ecclesiastical career track (also include lay members, same for monastic orders). Progress:
1. Novice
2. Sergeant
3. Knight
4. Knight Master (akin to Abbot)
5. Knight Grandmaster (akin to Arch-Bishop)
Some basic ideas. I have not seen much discussion of crusading orders, but I think that you ought to be able to grant baronial fiefs to the Templars, Teutonics, and so on. Historically, the Templars and Hospitallers owned large numbers of fiefs and other varied real property outside of the Levant, which in turn supported their efforts against the Muslims. The Teutonic Knights came to form their own state, more or less within the HRE, while the Knights of Santiago in Iberia owned considerable holdings as well.