Noob needs clothing help

I am an extreme newbie. I am so new, my bike is still a trail virgin. I need clothing help.

First of all, I don't understand jerseys. Why jerseys and not something else entirely? The ones I have seen in stores seem extremely thin. The jackets I have seen in the stores seem very thin too. Eventhough I live in San Diego, I run cold, so I am worried about buying clothing that will not keep me warm enough. On the other hand, I don't want to be too hot either, once I get going. I am leaning toward capris for the shorts, but I don't want to spend $100 on shorts.

Can anyone make some specific suggestions (brands, items) for layering?

Thanks for any and all help.

Speaking only for myself...
I often like to wear thin soft merino wool base layer tops when cycling, for various reasons: they help regulate your temperature, they don't get as smelly as polyester or lycra, they breathe and wick sweat away from you, dry quickly, and they don't feel cold and clammy if you sweat. SmartWool and Ibex brands have lots of fine soft merino for layering. Or you can get thrift store finds.

The non-wool tops I do wear are screaming neon yellow when I want to be very visible in traffic. Or I might wear a thin merino top and a screaming yellow windbreaker vest over it.
Many people like jerseys with big back pockets, especially if they have tiny bike bags. I like to keep my stuff in a roomy saddlebag on my bike instead of in pockets.
There's no law saying you have to wear a biking jersey to ride a bike. ;)
Wear what pleases you and feels good!

It does depend on the temperatures you ride in, but layers are good, since you will find that you get very warm and sweaty as you warm up, even on a cooler day. Multiple thin layers are much more effective than one thick layer. Thin layers trap air, which warms you up. A good rule of thumb is always to start out a ride *slightly* cool (unless the weather is warm, of course!) If you start out in cool/cold weather warm, you'll overheat rapidly, but if you can put up with a couple of chilly miles early on, you'll be much more comfortable later, and not have a lot of extra clothes to carry along with you.

Bike jerseys are nice because they have front zippers for ventilation as you warm up and pockets in back to carry stuff (snack, bandanna to blow nose, whatever...) They also tend to be rather form fitting, which is good on a bike. Don't need lots of extra flapping fabric acting like a sail. They are also typically constructed of quick-drying, wicking fabric, good for sweat!

As far as brands, I find Shebeest, Terry, and Pearl Izumi to be flattering for a woman's shape and come in cute styles and colors. Jerseys are definitely not unisex, and most men's jerseys are too long and not cut right for women's bodies. The elastic at the bottom rides up on our hips. Our forum sponsor here, Team Estrogen, is an excellent place to purchase great women's gear -- and they have good sales too!

But, wear what you like. There is certainly no rule that says you must wear jerseys. On my mtb I don't need the rear pockets since I use a camelbak, so sometimes wear wicking fitness tops (for runners, gym, etc.), and those work fine too.

If you are in a mild climate, arm warmers and a light wind vest are excellent investments. Everyone has a different thermostat :D, but I can get by with a light jersey, arm warmers (which may get rolled down if I'm working hard) and a vest down to maybe 50 degrees. I also think knickers are a great purchase. There is a real temperature range (for me at least) in which shorts are too cold and tights are too hot. For me, that runs from about 40-60.

In in-between weather (low/mid 40s-low 50s), instead of a long sleeve jersey (which are often quite warm, even if they are not thick and fleecy), I will often wear a longsleeve silkweight long underwear top underneath a short sleeve jersey, kind of like BSG does. Sometimes I'll throw arm warmers on over the baselayer.

Jerseys... I like them because I like the slim fit and the pockets. Obviously, you can find other athletic tops with a slim fit, but I find I really do use the pockets -- for tools, for cell phone and wallet and lipbalm (which I need to put on frequently while riding), and sometimes for snacks.

Jackets... you don't want an insulated jacket unless it's under 40 degrees -- in fact, probably not much over 35. Otherwise you'll sweat and get cold. You also don't want to wear a waterproof jacket in warm weather unless it's raining and you have to, for the same reason. Light wind jackets make a big difference.

You can definitely buy strategically and get a few versatile pieces that serve you well instead of buying an entire wardrobe.

I also like a rather tight fitting mesh undershirt (mine are from nalini) in anything but hot weather.
They ain't sexy but they pull the sweat off your skin. Prevents you from getting clammy.

I am relatively new to biking and didn't want to spent a lot of money on specialized clothing until I know what I need. At the suggestion of someone here, I got a pair of bike shorts (Shebeest) and wear them under regular clothes -- capris if it's warm, stretchy pants if it's cold. That has worked very well for me.

Pam