Honestly the first thing you should do, as others have said is make sure your headlights as usefully as bright as possible.
As for auxiliary lights, there are three basic kinds of "lenses" or types.
Flood- wide pattern, shoots light pretty much everywhere, so it doesn't go far, but lights up both sides of the trail really well.
Spot, or "pencil beam" - usually 5°, maybe 10° spread. Shoots pretty much straight forward only, nothing to the sides
Combo, "euro", or "driving" - a mix of the top two
Floods are good in tight, windey trails, where you are constantly turning so directly in front of you there is always a tree or bush.
Spots are great for clearer more open areas, think of them as an extra set of better high beam.
Combo lenses mix the two, usually because its cheaply designed and manufactured. They are trying to be spots, but doing a bad job and just throwing light everywhere.
If floods are what you need, get something cheap off Amazon with good reviews. It's easy to manufacture a housing that is super bright and just throws out light everywhere.
If you want longer range then pony up the cash for a name brand. I like diode dynamics, high quality yet cheaper then the others. They are easily double as useful as my high beams in the desert. The optics involved in making a tight pattern, long reaching light are much more expensive. If you find an ebay light that calls itself a "spot' for a good price, it isnt really a spot.