Before using a gambling website you need to check the customer support of online casino. If you are going to play frequently on a website, it is important that you do not ignore this feature.
Customer support button may be present but the support team may be sleeping or non-existant.

Its important to maintain the support team as well. Not every casino can afford that. But you can see the top ones like Primedice does so.
Researches of the whole site would be better instead of focusing on its customer support. Customer support does not guarantee that the site is a good place to spend your money. At least try to find some valid reviews about the site where you are going to play.
Regular withdrawals without hassle is what needs to be focused on. Often the casino needs to verify documents in order to pay. If this happens then you are sure to get into some sort of mess. The concept of anonymity should be maintained properly in the crypto based casinos which is often lacking.