I'll throw in a plug for a hub generator powered light. This is the most expensive option initially because you have to buy or build the hub into your front wheel, that'll mean at least new spokes in addition to the hub. But the convenience of never having to worry about batteries! Unlike the old sidewall generators, the hub generator doesn't slow you down.

It doesn't blink and if you want the convenience of no-batteries for a blinky as well, try reelights. They are pretty easy to install, you just attach the magnets to your spokes and the light goes on your wheel.

Regardless of batteries, magnets, or generators, multiple lights are a good idea. I don't know how many times I've found myself out in the dusk or dark and realized that one or more of my lights needed new batteries or had lost a connection or something. By the way the reelights are the exception to that. I have NEVER found them inoperable. They last forever!