question about yn-560

Will I be able to usr this strobe off-camera with my pentax k-x?
Should i buy anything with the strobe at the beginning (modifiers etc.)? I'm beginner so i have no clue.

Will modifiers for this strobe fit other strobes (both nikon and canon strobes)?

IF you remember it is a manual flash so it will not set the power levels for you. I have two of them for my Canon and use them in softboxes and umbrellas. Get either a sync chord that will go from your hotshoe to the flash or if you want to avoid the chords, you could also buy a cheap set of radio triggers. I like flash zebra for the synch chords. I believe the flash manufacturer Yongnuo makes a set that inexpensive and many here like them. I think they are called 602 and 603.