I wish I would have bought double the ETH I did when it was at $84 a coin. I got a $100 worth when it was at $84.62 a coin. I intend to HODL it till it goes back up over $400. After it reaches that I'm going to get more TRON with it. I have been using Binance for my exchange. I'm US-based, so I have to buy ETH through Coinbase then send it over to Binance to exchange for TRON.
Buying the exact bottom and selling the exact top is almost impossible, don't sweat it.
You bought at 100 and you're gonna sell at 500 - you're already extremely lucky, don't be mad if someone bought at 84 and someone is gonna sell at 650.
The important thing is to be CLOSE to the bottom and CLOSE to the top.