dont ask when you should buy or sell.
But ask yourself whether you want bitcoin or not, and if yes, then just go buy it.
Don't buy if you don't want it.
You can't time the market. You can not predict the bottom nor the top.
Then, after your first buy, you know your price point and you can start playing with it. Set marks respective to your buying point on when you want to buy more. I always buy more at 50 % drops from my initial point, if I still feel like it.
I also buy more when my expections have gone up 100 % but the price has only gone up like 30 %. Then that's a good deal to buy more at a 30 % increase.
If price has gone up 30 % but my expections of the technology have only increased 10 %, I will not buy more.