buy buy buy BTC~~

You may be be very right but I am worried that BTC price when rising too high , I do not know when to sell. I think maybe 600 is good, then I think maybe 700 and in this dilemma I fail to actually sell it at best price most of the time

I guess this must be a problem for many long term traders.
I guess just by buying bitcoin will not guarantee you'll be wealthy. but maybe when you're using bitcoin that you have to play a trade, and use bitcoin large in the trade, chances are you can get a greater profit, and make you richer quicker
you can become rich just with buying bitcoin, but when bitcoin price is low and you have to buy as much as possible. and wait a few years for the high prices. it's all very possible.