Anyone have a good recommendation for an entry level mountain bike? Kid just learned to ride hers and on the same day is already cruising at its top speed and going off road to a small degree. Looking for something quality that when can grow into as she gets better. budget is 300-$500 looking primarily used. Current top list include Diamondback, Trek, GT. Thanks in advance

REI's Co-Op bikes are decent.  My son has one, he is 11.  Has a front suspension and hydraulic disc brakes.

We have an REI for my 6 year old as well.  It has good components for the price.  He seems to like it

Any of the major brands in your price range should be decent.  Trek, Specialized, Cannondale, Marin, REI, etc.  Probably be closer to $500 than $300.  You might want to consider something without suspension at her age to keep the weight down.  A lighter bike will be easier to handle and much more enjoyable to ride for a kid

Looks like some are on sale ar REI

https://www.rei.com/product/143201/co-op-cycles-rev-drt-kids-bike

https://www.rei.com/product/143168/co-op-cycles-rev-20-6-speed-plus-kids-bike

There is also a Mountain Bike subforum in the "General" section of this website where you may get more views

I've had two Treks but that was almost 30 years ago. Wifee doesn't believe in exercise. One of many things she felt was stupid!

Used is the way to go

Picking up a bike that is 5 years old that was $2000 new for 3-500 is not uncommon in my area.  Shop Craigslist or Facebook.  This will be much better than buying a $500 new bike- no comparison.

Take her along and look for someone who is a serious mountain biker who is upgrading.  Some folks have to have the latest thing every few years and there are some great deals to be had.  You won’t find many dishonest bikers in my experience, especially is they know the bike is going to a kid.  I have probably bought 10 bikes worth $2-5000 each for the kids over the years and never been burned.  

I am partial to specialized, but there are lots of good brands out there.  Google whatever you find and see what the original price was.  You are basically paying for lighter weight and better components.  If you get something that retailed for $2000 to begin with and doesn’t have any issues it doesn’t really matter much what the brand is, you are going to get a good bike with decent components.


ETA. I should have asked how old she is.  If she is very young, the above doesn’t apply, obviously.  If she is 10 or older you likely can find a used bike from a small woman that she can grow into.  Don’t go too big too soon, or she will be handicapped and might get frustrated.

Take a look at Bikes Direct as well.  I have their Gravity model and it' served me well.  I'm not hard core downhill, but it's held up well.  Their tech is not new but over value for the price.

Bikesdirect