my colleagues want to start trading in cryptos and they want me to suggest a site that is the best to start trading, but i dont what to answer because there so many cryptotrading sites. So for you guys what site and app do you think is the best?
Do your colleagues know something/anything about trading? Knowledge and experience is most important, then you can look for trading sites or apps. I guess they want to buy crypto with fiat, if this is a case exchange need to have that option. Binance for instance(like Poloniex) is not support BTC/USD at this moment, but after they open headquarters in Malta this could change. But for just crypto pairs trading most users agree Binance is best choice.
If you need to buy crypto with fiat then try Coinbase ( it is USA based exchange), or Bitstamp (based in EU), but some users say they ask too much data for verification.
It is very important to read TOS before you start to use any exchange, there is rules that every user must uphold or account can be frozen at any time.