Which is the best exchange platform to use ??
It all depends on your region, the coins you are interested in, etc...
I personally am using Binance, Kucoin and CoinExchange. The last one, cause it has new coins faster and these can grow a lot when they hit Binance.
I also have an accoint on Cryptopia, but never used it, and I am verifying my account at Kraken, to convert it again to Fiat money.
Mostly it will base on the region you are from, And it will certainly involve some exchange depending on your country on what exchange site that is perfect for you, There are many exchange site to choose from and I am using Poloniex, CoinExchange, Or if you have ERC20 you will use Etherdelta for your tokens.