I think that you need to be much more specific in your impression goals here. To begin with, what class of Californio do you want to do? There are not many period pictures of Claifornios. By the time cameras made it to California, the Californio life style was under a great deal of pressure. There are paintings of Californios but they are of the highest class of society.
For example, below is a photograph of General Don Andres Pico (brother to Pio Pico, last Californio Governor of California) who was one of the few Californios to do very well during the American period, he became wealthy ranching and farming. Notice that all of his clothing is dark, black and dark blue were popular. The clothing is a variation on the Traje de Charro, which derives from the traditional horseman's clothing of Slamanca, Spain. The traditional clothing is brown but in Mexico and California a fancier "dress" version of this clothing, known as the Gran Gala Treje de Charro, became popular among the elite (later Emperor Maximilian would adopt it as his state clothing). This version of the clothing has given rise to the traje de mariachi, the black or sometimes bright colored suit worn by mariachi bands. One note, in the period, bright colors were not commonly seen, if they were used at all. The dress suits tended to be black or blue.
Anyway, you will notice that General Pico's jacket, which is heavily decorated with embroidery of bullion, is well fitted with relatively thin, long arms and a standing collar (indicating that this is actually a military dress jacket). He is wearing a vest, a white shirt and a tie under the jacket. More distinctive are the pants, which like the jacket are heavily decorated with embroidery and held together along the outside by a series of buttons, commonly of silver. Note that they are unbuttoned up to the mid thigh showing his white underpants. Interestingly the inside if the thighs are of a different color. This could be a riding seat (a reenforcement of that part of the pants which come in contact with the saddle) but it is impossible to know what color it is. This style was very popular in California at the time though this is obviously a very high status individual.
Below Pico is a painting of Don Jose Sepulveda (who owned one of the most famous ranchos near Los Angeles) painted in 1856. Although the suit he wears is much plainer then General Pico's, it is essentially the same. One difference is that the coat does not have a standing collar. You can clearly see the buttons along the leg and a flash of the white drawers. Also note his hat, known as a "sugar loaf" this style of hat was the most common type seen on Californios. The key thing is the shape of the crown which got its name because of its similarity in shape to the cones of sugar in use at the time. The size of the brim varies greatly over time and due to taste but the sugar loaf is the distinctive hat of Californios of all classes. Note also that Don Jose is not wearing a gun. Californios were much more likely to use a lance or the sword which is visible attached to the saddle in the painting. This sword, was a common feature of Californio saddles and you will still see a short sword or machette on many modern built Mexican saddles. While in military service a Californio might wear a sword belt ,but in peace the sword was on the saddle.
Although these photographs are of high status individuals, the basic cut of their clothing would translate to lower class individuals. Instead of dark clothing a working class charro would wear a sort of tan or sometimes light gray. Charro clothing was first adopted by the working class in Mexico in the 1600s when peons were given the right to ride horses. In many ways it has not changed much as the actual charros are very traditional and resent others wearing or modifying charro clothing (they hate mariachi bands). The basics of working class clothing would be a jacket and pants like that worn by Don Sepulveda with several additions. One would be a pari of botas de alas, seen below. Spanish for "winged boots" they are short coverings for the lower leg which act like chaps. Another thing might be a sash in place of a vest. The sash provides a distinctive flash of color and is cooler than a vest. You can also stick a pistol and a knife in the sash. If you were to wear holsters you should have a straight up and down slim jim or what they call a bikini holster (which holds the cylinder but does not cover the barrel). For some reason the bikini style was popular among hispanic peoples. Take a look at the last painting for an example, Essentially the same clothing as Don Sepulveda in brown, a pair of botas de alas, a sugar loaf hat, no vest, large california spurs, also notice that he is not wearing a gun.
On the topic of knives and pistols, the 1851 Colt Navy was the gun of California in mid 1850s and early 1860s. The 1849 pocket model and Allen pepperbox revolvers were earlier, obviously, but once the 1851 came out it was very common in California. Depending on which program you are doing in Old Sacramento, the authenticity people will not let you carry a ruger, and frankly you shouldn't do it even if they did. Bowie knives are an American phenomenon and you would not find them on a Californio. Why would they want one, they have their own style of knives which is much more Eropean. Think European stiletto, thin, double sided and relatively long.
I spent a number of years working as a living historian at Sutter's Fort and we have been through all of this. if you would like more detailed information go to Sutter's Fort and ask them for the docents costume guidelines. It is not absolutely perfect but it is a good start to clothing during the Sutter period (which ends in about 1850) and does include some information on Vaquero clothing.
Hope this helps