I opted for a generator setup. While all of the lights I see recommended here look great, they annoy and often blind drivers. Nearly all generator lights have a high cutoff like a car headlight.
The best combo for gravel in my opinion is a generator light and a helmet light. The helmet light helps see low hanging branches and you can point it into a turn, which you cannot do with most mounted lights. For the occasional car coming the other way, you can simply point your head to the side of the road so you don’t blind the driver.
Gravel rides always take longer than expected, so riding with a generator doesn’t carry the stress of running out of battery. Using a headlamp also solves the problem of how to use a bike-mounted light for a road side repair.
The amount of light needed for most gravel rides is not as much as people think. Without light pollution from car headlights, signs, and street lights, I can run my headlamp o medium instead of high and still feel perfectly safe. Wet pavement and dirt is the exception, as it seems to “soak up” light easily.