My rule of thumb has always been that one should spend as much on the optics as he spent on the rifle. That is, $1200 rifle gets a$1200 scope. If you can’t afford that, you can’t afford long range shooting, and we haven’t even started talking about ammo or real training. You’ll be much more successful if you follow this.
My rule of thumb is based on the distance. If you are going to be shooting at 200 yards, a $200 scope will do. $1,000 for a 1,000 yard distance.