There are a lot of longer zoom options you can look at later. Frankly, I never found the 50-200 to be long enough when I had one. That doesn't make it a bad choice, that was just my feeling about the lens. If you are completely new to this game, I would suggest the basic kit (camera and 18-55) especially if money is tight. There are other things you're going to need as well. Batteries, bag, you may find yourself lusting after a tripod, and all the other gazintas.
Get your kit, at least one complete change of batteries (8 total) a good charger, the card and maybe even two, something to carry it all in, a lens cleaning kit, etc. Then hit google, this forum, the library, and the great outdoors to learn to use your new toy. Key word, learn about Exposure (if you don't already know). If the kit lens with the Kx is optically the same as the one on the K7, it's actually a decent performer.
Now all you have to decide is What color!
Welcome to the Pentax dSLR club.