Hey there @proshack I would suggest Binance, which I have used mostly. Otherwise Kucoin exchange. There are other good ones but I have not used them much, only herd of their names, like Poloniex, Bitrex, etc. They are known to be reputable too. Long term buy and hold on BTC or ETH is a safe investment. Or are you interested in day trading? It is more risky and takes more of your time, but it depends on your personality and lifestyle. What is your strategy? I'm always keen to chat about trading and crypto.
Best wishes