OKEX is centralized exchange which allows to exchange a standard set of crypto. They implemented also options, margin, savings etc. as many top tier exchanges. One of the best things for beginners is their BTC daily program for learning in their academy. This could after some time earn you a good portion of BTC. The volume of the exchange is reasonable so are the fees. I have one bad experience that after you have recived a bonus the withdrawal fees are temporarily higher than usual (there is no information about this policy at their website). From my personal experience the support is rather worse (not supportive) than market standard. I am also lacking their own fiat gateway.