If you come to the Netherlands then of course you must visit Amsterdam. The capital of the Netherlands with its finest museums and other sights is also worth a visit for Dutch people, by the way. What is there to do:
But, of course, there is much more. Want to see it all? Then you may also test in the purse because with an average price of more than 20 euros per person per attraction, it's going to quickly get into the papers. Or can you help with some discounts?
If you are a resident of the Netherlands, you can buy a museum card for a few tens that allows you to visit just about any museum in the country. As a tourist you don't have that option, but there are a number of other ways to get a discount:
Crossing Amsterdam by car is not really an option. If you stay in the centre, walking is a great option, but as some outings are quite a bit away from each other, it's nicer to take the tram. Then you can buy a separate ticket each time, but there are also plenty of providers of "unlimited OV" tickets. For example, this card from GetYourGuide that gives you unlimited use of public transport for 1-3 days (including from Schiphol Airport!)
If you've been to Amsterdam, you must take a canal cruise. You'll see the canals, beautiful stately houses and bridges while a guide tells you what you'll see. You can board a boat at almost any place. So there are deals from 45 minutes to about 2 hours. Includes snacks and drinks and with or without a guide. Some great deals can be found here.