I think $5k-$6k buy range is good. If it dips below $5k that's fine but even buying above $6500 is imho a bad move unless you're buying and selling constantly to make 5%.
It looks like we're too late to buy bitcoin for $ 5- $ 6k, seen in 3 hrs bitcoin never dropping below $ 7500 and now priced close to $ 9000, but I think any price is good because a few days the bitcoin price will reach $ 10k.