Although hundreds of casino's are open to Dutch players, none of them offers paying through 'iDeal' .
This has to do with the upcoming regulation per September 1st.
Almost all casino's offer paying through 'Trustly' or 'Klarna'.
Both payment options work the same as iDeal.
In almost 100% of deposits your money goes instantly from your bank account to the merchant and appears in your casino account.
When you signup at a casino, you'll probably be offered a (welcome) bonus.
There is some value in taking bonuses, but bonuses come with Terms & Conditions that you'll have to adhere to, for risk of losing your money if you don't. More often than not the casino bonuses are geared towards playing slots on low stakes. If you deposit for playing blackjack at Live Casino, you are probably better off not accepting a welcome bonus.
I don't play at N1 Casino myself, but I found the following in their Bonus T&C:
The maximum bet while wagering is 5 EUR or equivalent (5 USD; 50 NOK; 7.5 CAD; 400 RUB; 20 PLN). The max. bet limit includes bets doubling after a game round has been completed and bonus rounds (purchased within the game).
So, even if live blackjack play is allowed while playing with a bonus, you should never play higher then EUR 3 per hand because when you double down or split your cards, you are breaking bonus T&C.
That said, enjoy playing!