^
Totally agree. When I'm alone, I always have my red blinker on regardless of day or night. Many of these lights have several modes such as always on and blinking. I typically having it on blinking as it should attract more attention than just a red light that's on.

Other than that, everyone else has made some good suggestions for items to carry. I would like to add that a good pair of bibs or shorts goes a long way in the enjoyment of this sports. It's something that I've found worth splurging on. My first pair of shorts were from the clearance rack at Performance Bike and while they were okay (and I still use them on the trainer) the chamois started to get flattened after a few months of riding.