Crypto market is go down in this movement. I have some USDTs. So I want buy some coins. Is this time good for buy? What are the good coins to buy and Hole long term? Any suggestions?

The market is really very down. Down market is very good for invest altcoin. $500 availble for invest to Ripple. I like to invest for getting good profit. I have more than 50000 Dogecoin also.