The good thing with most Crypto exchanges (like Bittrex) is that the fee which they charge is in the form of a percentage (Bittrex charges 0.25% per trade). This means that you can begin to trade with as little coin as you want! however, you must take into consideration the minimum trade value of the exchange (Bittrex requires a minimum trade value of 50K Satoshi).

BTW: I use Bittrex as the example because it is the exchange that I use and the exchange that I recommend you to use.

Good luck and stay safe!