What Gizmo99, said. I lived and hunted in Kalif. for 35 years. Used a whole bunch of calibres, but if I were choosing JUST ONE, I'd go with either a .30-06 or .308. (My favorite calibre was/is .280 Remington.)
Buy the best scope you can afford. Because of the Kalif. terrain, in which you can get some really long shots, or, some very close brush shots, I'd opt for a variable scope with a 1 1/2x 5 power, or something in that ball park. I'd rather put a $400 scope on a $100 rifle, than vice versa.
FWIW. J.B.