For any coin the easiest way to figure out where to buy them is by going to coinmarketcap.com, opening the crypto you're after and clicking on the Markets tab. It'll list the exchanges you can trade for it in order of volume.
I use Bittrex, but apparently they aren't accepting new registrations so likely Binance is second best bet (though they don't have NAV Coin). I don't trust Binance as much as Bittrex, although I've used them before if there is a cryptocurrency unique to their exchange. So basically... Bittrex & Binance.
Bittrex and Binance
For any coin the easiest way to figure out where to buy them is by going to coinmarketcap.com, opening the crypto you're after and clicking on the Markets tab. It'll list the exchanges you can trade for it in order of volume.
I use Bittrex, but apparently they aren't accepting new registrations so likely Binance is second best bet (though they don't have NAV Coin). I don't trust Binance as much as Bittrex, although I've used them before if there is a cryptocurrency unique to their exchange. So basically... Bittrex & Binance.