those reflectors don't do much when the traffic is approaching you from the front or the back...that is why most people get rid of them. I don't like reflectors in general; by the time the light hits them the car is already too close to me .
LED blink lights are the way to go if you are finding yourself in the dark.
I completely agree with broadbill. The reflectors may be good in limited situations but I would not rely on those solely to be seen. I ride the hills of west Philadelphia which are heavily traveled and quite congested. I use the blackburn flea usb front and rear lights, both set to flashing. They can almost blind you if you stare at them from a close distance, and my wife told me she could see me at dusk from about 1/2 a mile away.
There are certain investments I consider essential when biking, specifically a good quality helmet, lights and routine bike maintenance. Once those are taken care of this can be relatively cheap (okay...maybe better said affordable) hobby/exercise program.
Here's a link to those lights I mentioned.
Blackburn Flea USB front headlight
Blackburn Flea USB rear taillight