TL;DR your sole option is to register as a creditor of WOW air with the curator/liquidator of the bankruptcy. Unless you bought additional insurance on your ticket
First off, if you have an (ongoing-) travel insurance ((doorlopende-) reisverzekering), is to call your insurer and ask what they provide for bankruptcy of a travel agent. Usually your bank is also the travel insurance provider in the Netherlands. I'm not optimistic; this SkyScanner article suggests that bankruptcy is not covered in travel insurance, but at least they'll be more knowledgeable on the juridical side of things.
Seeing you paid with a Dutch debit card, which is entirely reasonable when you're Dutch, and have not taken out any additional travel protection insurance (at least, that's what I assume, since you didn't mention it), there's only one way forward as far as I can see: make sure you are a registered creditor when the bankruptcy files (see e.g. this news article). phoog's answer has a collection of official links where the legal curator should be annouced.
You will most likely not be the only Dutch citizen having this problem, so probably someone will create a sort of rights-foundation where you can subscribe, and they will collectively try to get their money back. It means you loose some percentage to advocacy costs, but at least you don't have to go through the legal procedure yourself.
So keep an eye out for the bankruptcy declaration and who the curator is, and contact them, as well as any rights-foundation (belangenbehartigingsstichting in Dutch) which will probably be set up for all duped clients. You might see some of your money back, depending on how bad the financial situation was, but it will take years most likely.
As far as I can see the standard EU safeguard for flight cancellations, lost luggage, delays etc does not hold for bankruptcies. You could contact them of course, although I don't expect you to get a refund through there.
The usual 2 week term for sending back online-bought goods does not hold for travel tickets neither alas.
Why most of the other answers are wrong:
You have a Dutch debit card. What the international community here understands from the debit card principle is, as I gather it, some kind of prepaid or Credit Card-Light. Sadly, this is not the case. All the cashback mentions in other answers are, however hopeful, wrong. They simply do not work with a Dutch card. What you did was most likely an iDeal(1) payment (or an actual PIN payment with your card on Schiphol), which transfers your money from your account to the company, in this case WOW air, directly. There's no such thing as a payment company in between, so all the cashback tales you're thrown as a bone here simply do not work. Sorry, but your sole solace is trying to register as a creditor. Please, be my guest, try to contact your bank to get a cashback, but don't be surprised when they look at you weird. It's just not a thing with the Dutch debit card. As gerrit put it:
Terminology note: American "debit cards" are not Dutch "debit cards". In US, CA, UK, "debit cards" typically have a 16-digit number and CVV code, a magnetic stripe, and can be used for card-not-present payments. Dutch or German "debit cards" have no 16 digit number or CVV code, and increasingly often no magnetic stripe either. In US/CA this is often called an "ATM card".
Sorry, but the other answers are from an Anglo-Saxon point of view on the debit card which simply is not true for the Dutch case.
(1) From the linked page:
(...) this payment method allows customers to buy on the Internet using direct online transfers from their bank account.
Bank authorizes transaction in real-time, deducting the amount directly from the consumer's account (if there is not enough balance, the transaction will be refused)
Merchant received real-time confirmation of the payment by the bank
There is no chargeback right however, which can be considered a disadvantage for the consumer using this payment method.
I.e. your money is there basically the moment you confirm your iDeal payment, and no chargebacks are to be gotten.