It’s mandatory in the Netherlands to have a Health Insurance. This is a Personal insurance and not covered by your employer. Depending on your needs we would advice to do this as soon as arriving in the Netherlands.
Having a Credit Card in The Netherlands is useful for paying for your more expensive transactions. Also for online purchases Credit Cards are recommended. Depending on your Credit Card they are mostly protected with insurances. In the Netherlands you won’t find many places where you can pay with AmEx.