If you want to receive from a Sacramento county site, all you need is the 4 control channel frequencies in a bank. If you want to receive from a Sacramento city site, then you'll need those 4 control channel frequencies too. Now there is a trick to make the two sites work in one bank, but you'll have better control over what you are monitoring to use 2 banks. Perhaps you only need one of the two sites anyway.
Note: I programmed ALL frequencies for the city in bank 4, and all frequencies for the county into bank 5. They are all set to MOT. I leave all but the control channel frequencies locked out. Sometimes I'll just browse the frequencies to see what I can hear. Plus if they ever use one of the frequencies currently not designated as a control channel for a control channel, all I have to do is unlock it.
gmclam has some good ideas for you. Programming just the control freq.s is called cco, (control channel only) and has been around for some time now. Your most immediate learning experience after that will be deciding on how to arrange the talk groups. Obviously local conversations will be your priority. After that, you may want to experiment with high-priority assignments arranged in additional talk group banks like swat, narco's, tac channels, etc... I highly recommend getting the programming cable (should you more than likely have a pc) to make the task easier, and there's some good (free) software out there. Also having the additional benefit of saving your config('s) for experimentation. Just realize that your (radio) model doesn't support pc-control. Then there's the joy of discovering antennas', their design, manufactured vs: homemade, and so on. `Yup, you picked an expensive hobby. : ) Cheers, good-luck, and mostly, good-fun!