Euros.
If you donate 2e, you're gonna have 2 tickets at every draw. If you choose to donate 20e more, you'll have 22 tickets at the draws from now on, unless you choose to donate more.
Also paypal converts automatically from the currency you're donating to the currency that the one who's getting the donation has requested it to be. So if you donate in dollars they'll be converted to euros, I'm not sure about the course atm.