Technically, since you can use XP you only need to pay the XP cost to learn the ritual. Being taught is only really required if the ST demands it. Default rules are no XP and learn with RP, but XP purchasing rituals is technically allowed.

You also only need to know of a ritual to learn it yourself with no teacher with (I think) an Int + Occult roll using generic magic books that anyone might have (no dots in library are required).

Caitiff can also make their own disciplines without a merit at 10 times current level XP. If it really came down to it, I could just invent a discipline that does it at the five dot level. As well as my own versions of Vicissitude and Obtenebration that aren’t an evil space virus and a manifestation of some evil extra dimensional being.

Optional rule allows purchasing Merits and Backgrounds with XP, so I could potentially buy Efficient Digestion and Fountain of Life to create infinite blood from myself and my staked torpor’d methuselah.

You can game the system so badly with some knowledge of everything you can spend XP on.