I'm already familiar with coinbase and Gdax but they only cover four coins at the moment.
What is a good exchange where I could buy and sell alt coins like Ripple, Dash, Monero, and Cardano?
Ideally, the fees will be zero or very low. Obviously I want something secure as well.
No Doubts that lots of no. Of trading sites are available to make trade but I am sure that you will find that mostly every trading exchange are charging the same type of fee for trade ( buy and sell ) but if you want to go for better security then my suggestion for you to use bitfinex as a priority Because in my opinion bitfinex is better for giving security .
But not every coin you can get at trading site , may be few will missing and that will be available at another exchange .
Here overall I mean , you should have accounts at every trading sites Because if you will have bitcoin at every trading site then you can do exchange to exchange trading ( difference in price of coin from exchange to exchange ) .
What makes bitfinex a more secure exchange than others? Or do you just think it has to be better secured because of the amount of btc they have?