There isn't much to look into. Gambel's is widespread countywide. You could go your whole life birding in Orange County and never see any other subspecies. Pugetensis is restricted to the coast and still rare there. Their bills are yellow and they have a general brownish wash to them. We rarely get dark-lored birds, presumably oriantha given how close their range is although leucophrys looks nearly identical, and those have dark lores, dark supraloral areas, and reddish bills. We occasionally get intergrade birds that appear to have Gambel's mixed in and that have dark lores but no dark supraloral area. Nuttall's doesn't occur here at all, they're non-migratory.
You're more likely to find different subspecies of Dark-eyed Juncos and Fox Sparrow than you are White-crowned Sparrow in Orange County.