If it’s a cheap Chinese, you need one that says 10 meeeeelion lumens.
Might then be about 1000 😉
I’d say 1000 to 2000, but you want that at its general use setting. If it’s only that figure when on highest then while bright it will drain the battery in no time. You want good lumens at a setting that will last a ride.
Also consider two lights. Bar and helmet. You don’t need crazy lumens on each then, but combined they put out enough and a helmet light points where you are looking which is critical for off road twisty trails. Ideally get one more of a spot focus for helmet if you use both bar and helmet.
Group rides, you need to compete with the others. Once you’ve gone forest burning power, the others will then up their game and go brighter than you.