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or can I start with GK2? Thanks
This question / problem has been solved by BassForeverimage
brento: or can I start with GK2? Thanks
I'd suggest playing GK1 before GK2, many elements of GK2's plot assume you've played the original and already know the main cast of characters and their titles/jobs.
Read up on the Schattenjäger order while trying to avoid spoilers on the events of the first game. Then you will have a better understanding of who you are and why you are investigating the murders.
Well, personally I played GK2 first and didn't feel at all that I was missing something. Even though the game contains a few references to the events and characters of the first game, but the main story itself is totally new and doesn't need the knowledge of previous happenings. (Though - as Charon mentioned - it's good to know who the heck is the Schattenjaeger, but it's explained in the manual.)

That said, Gabriel Knight 1 is still an excellent game - perhaps the best in the whole series, though Gabriel Knight 2 is almost as good -, so even though it's not necesary, but you should still consider to play that first for the best experience.
thanks everyone, i'll definitely play the first one first!