Should I buy BTC on 6500, or wait to possibly go even lower?
Yes you should buy BTC on 6500 because by the end of this year bitcoin will go up up to 10k $ so what are you waiting for. Buy now and be a millionaire tomorrow.
If he's still not buy yet, he will make more profit in next time. I thought bitcoin was no less than $6500 yesterday but I was wrong(now it's only $6200). But if he buy at $6500, it's no problem because you're right "buy now and be a millionaire tomorrow".