As stated earlier, you do not need the frustration of being alone in a cabal as a new player. Cabals grant extraordinary gifts, but these gifts have strings attached. When you pick a cabal you are likewise choosing an enemy.(Heralds Excluded)
When you feel you can hold your own in PK as you do in RP, I feel Foxx has given you sound advice, choose a cabal that will have active mentors to guide you through the various duties you will be expected to perform. Whether those duties are the movement of cabal armies, or taking the head of some poor sap who has gotten himself on the Top10 list.
If you go into a cabal that has few or no active characters, you will find yourself standing alone against the tide of war. Meaning you will have many enemies, causing you to be outnumbered on the battlefields, or hunted like a dog if you choose a cabal that does not have armies. Choose wisely and good luck. My first was a Savant, some say go Warmaster to learn to PK, but if you think about it, Savants have to fight Warmasters constantly. Six and half the dozen.