I did something like this a few years back. Had a 32 pounds $805 full suspension bike. Believe it or not, I was able to claim top 3 in all segments of a local cat 2 climbs with it.
But when the fun starts on the downhill, my other better bike brought more smile after each ride. The brakes were safer, suspension much more compliant when it got rough. You can see how much smoother Neil is over the roots and drops in the video.
Eventually I upgraded almost everything on the $805 bike to make it ride better. In the end I should have bought a 3k bike to begin with because thats how much it takes to bring the cheap bike up to par for the bigger rides.
To be fair, for a cheap bike, it was pretty decent for most tame trails beginner would ride.