The kits generally include a bunch of stuff you won't use and you will need to buy some caliber specific stuff that's not in the kit.
Get a pistol rod, 9mm jag and brush, .45 jag brush, cotton pistol patches, the bore solvent of your choice, a GI toothbrush, some light teflon oil, and maybe some Tetra grease. I like a little grease on the slide rails instead of oil because when you carry the gun all the time, the oil runs out the muzzle end after a few days. You should be able to buy all of this for around $20 at any gun shop or Wal Mart.
Cotton swabs, rags, tooth picks, and a can of compresssed air will also come in handy. Boresnakes are really nice, but I tend to use them more on rifles. I also have a bore light, a dental mirror and pick set, and keep it all in a cheap little plastic tool box.