Here are some good choices for lights. You want a minimum of 1,000 lumens. Lumens are pretty misleading but the name brands (Trek, Bontrager, Magicshine) are pretty accurate. But the generic ones you find on Amazon vastly overstate the lumens.
The lights with self-contained batteries are easier to manage than ones with cables that attach the battery to the light.
I'd recommend starting by checking out the lights at Trek Bee Cave. They have a good assortment and the Bontrager lights are great quality for the money: trekbikes.com/us/en_US/equipment/bike-accessories/bike-lights/bike-front-lights/c/E416/
Here are some cheaper options from Amazon:
Front + back kit <$40
Brighter bar mount with external battery
TREK Full Suspension 25% off listed prices with NICA discount
TREK Hard Tail 25% off listed prices with NICA discount
If purchasing used, our minimum recommended specifications: Disc Brakes, Front Suspension, 1x11 or 1x12 drivetrain, Tubeless wheels and tires. You are looking for "cross country" or "XC" category mountain bikes. Cross country bikes have geometry, suspension travel, and weight combinations that enhance efficiency of effort through a variety of terrain.