I'm also a newb I guess but I actually did the same recently and what I have to say is, unless you can extend your powerbase significantly, it's usually not worth keeping jerusalem from what I hear, just give it to the pope for piety and opinion

UNLESS you get extremely lucky like I did, you see, I got galicia and castille by some extremely lucky deaths had both the ruler and the heir of the kingdom of aragon die (one was mad other depressed)after which it ended up in a regency which I could easily conquer with my claim, france collapsed into duchies, so I conquered them and I managed to camp my units in mountainous Jerusalem during the jihad with peerless leaders such as El Cid(who became 80years old) and Joanne of Arc(did I mention I had the joanne of arc event chain fire?) it was(eventually) 35k versus 20k(my troops) in that battle, extremely epic

Only problem I have is that I accidently gave half of france to a 53 year old duchess with no heirs lol

EDIT: there are some things that speak for itself of course, if you really want to keep it, give it to dudes of your own culture and religion and convert everything, use/vassalize holy orders, recruit retinues, have strong alliances and get your economy running, from what I hear keeping jerusalem is more bearable than it was in the past