Revolut supports holding balances in 24 currencies - EUR, USD, GBP, JPY, CHF, SEK, DKK, NOK, PLN, HUF, RON, TRY, ILS, CAD, AUD, NZD, HKD, SGD, ZAR, MAD, QAR, AED, THB, INR.
One of the best things about Revolut is that you can exchange money from your home currency to the currency in which you will be spending. It is extremely unlikely that the exchange rate will be optimal at the time you use the card to spend at merchants. Therefore always exchange money to the destination currency in advance. The most liquid times and consequently the best rates will be during business hours of the destination currency. Avoid weekends when the FX markets are closed with no live prices; Revolut gives you Friday’s closing rate with a markup of at least 0.5% to protect itself against any movement before Monday morning.
By watching the exchange rate over several days, you should be able to pick an optimal time to buy your destination currency. The only time you should spend in a supported balance currency directly from your home currency is when the destination currency is devaluing fast intraday. If your home currency is devaluing fast (as has happened with GBP), then buying your destination currency in advance becomes even more important.