Usually you want to wait for a dip before you buy. However, sometimes it's still a good idea to buy if you think a rally is about to break out. Do research, see what smart traders are saying on twitter for a little help. Try analyzing the charts. Personally, I think it will break 8000 and go up to 8500+ within a week. I still would rather buy Eth though, I think it has more room to make gains.