A bicycle co-op can be #1 , a great place to get some things inexpensively and #2 , have someone teach you how to do minor roadside repairs.

I carry a patch kit, a pump and a spare inner tube. If it's really hot or raining I just take the punctured tube off the wheel, check the tire fro sharp debris (a cotton ball works great for that) and put the new tube in. then I patch the old tube at home or wherever I'm spending the night if on an overnight ride. A rearview mirror is quite helpful in traffic. I use a takealook mirror on my sunglasses or a helmet mounted mirror.

Oh, some bike shops host basic repair seminars or might make arrangements to teach you.

Cheers