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? 
If you still have more capital lying around go for crypto which has gone down 90% or more even with great potential. Coins like Nano and DeepOnion are some. They are down because they were distributed freely and people have misused them. But Nano has a top notch technology and DeepOnion contending to be top privacy coin with DeepSend releasing soon. So only way is up. Do not buy pump coins which are mentioned by youtubers. They are usually sponsored and will be dumped unexpectedly.
Always buy the ones which are oversold.
DYOR
Good luck