At the risk of starting a helmet debate, your helmet's going to be very little use if someone drives through you at 40mph. I've got various hi-viz kit around, mainly from motorbiking. I've always worked on the basis that one light is a bare minimum but what if it fails or gets mud splashed on it? And I don't think the "drivers don't pay attention" argument really works for that matter, a single light just isn't massively visible, you can easily do better. I do the same dark road commute by motorbike and by pushbike and some of the stealthy cyclists you see with one light are easy to miss, especially in traffic.
A lot of stuff sold as visibility gear- the classic sam brown belts etc- aren't much good, so that's one thing to watch, 3M retroreflectives or a similiar product are what you want, if you're going to wear anything, don't settle for old-fashioned reflective strips and yellow cloth. A builder's vest is great for cycling, since they're also very well ventilated, and dirt cheap (one with arms, better still)
But if you don't want all that, and you wear a rucksack, a couple of 3M adhesive strips costs buttons and does make you immensely more visible.
) was banging on about last year...
