My suggestion is you don't have to start on bitmex if you don't know about stop-loss, you can try with Binance or other exchanges which will easy to understand. Besides that, you need to read more information, and if necessary, you can watch a video from Youtube.
I dont know bitstamp because i do not have an account there. But i see they charge a fee of 0.25% per order.
If you can stay away from sliding the leverage bar and obky use 1x limit orders, than bitmex can be a lot cheaper to trade on because of the taker fees. Bitmex has a lot less choice in coins to trade, which for a beginner i think is good because it prevents from overtrading on a large choice in different altcoins.
Whats your view on that?
If you use Binance, you can use BNB coin as your trading fee which will cheap than btc, and you can found so many coins to trade which will give you more chance to make a profit.