Entry Level Mountain Bike?

So im getting into mountain biking but i'm not a total noob and I am looking for a bike that isn't the nicest in the world but will perform much better than a walmart bike. I mostly ride singletrack, and i'm not looking for a FS bike because those are out of my price range. I'm trying to cap my spending at about 500 on the bike alone although i'm open to any suggestions. If possible i need 100mm travel on the forks.