With Revolut, you can get a free MasterCard payment card that you can use to send (top up) money and pay anywhere - online or physically. If you register through the above link and verify your account, you will receive 300 CZK as a welcome gift. I did too :)
In addition to being safe (the card is not linked to your bank account) and having many features (savings through rounding up, sending money to friends including GIFs…), the main advantage for me is favorable exchange rates.
For example, the savings on USD compared to AirBance is around 0.40 CZK, and it’s even more with mBanka.
If you often shop at foreign e-shops (or travel), it is advisable to send CZK to Revolut and have it converted to USD only when paying.
The ultimate savings is when paying through PayPal (which has crazy exchange rates) - when paying, change the Conversion option so that PayPal does not do the conversion, but the card issuer does. You can add the Revolut card to PayPal like any other regular card.
During my last purchase through PayPal, this trick gave me a rate that was 1.23 CZK better for EUR, which saved me 90 CZK just like that :)