i want to start doing crypto trading
so what site should i use for it
i would want a site that has low fees
I always encountered with this same question for a newbie, well, as of now you can't make an account in bittrex, poloniex and binance recently they announced that they did not accept for new account member and the reason is to give better service to their member. Why you should not try in hitBtC so far that's a good site will now still accepting new account or you just wait for bittrex, poloniex and binance for their announcement when they are open for creating and accepting new accounts. In low fees i must prefer on binance, then happy trading good luck.

Binance is open for new account registration, not sure about bittrex,poloniex. i would advise one to stay away from hitbtc, lots of people are complaining about their deposits/withdrawals not being credited.
with i have to submit documents in these sites
can you trust these site with your personal info
Use binance, they don't ask for any ID. there's 2 BTC daily withdrawal limit though.