Guide my holiday Eurotrip 2p2

[RustedCorpse]

I’ve managed to secure a little extra cash, and a friend randomly suggested that we go to Amsterdam for about a week and a half. What was first a joke seems to really be taking off into a full Europe trip. At the moment we’re looking at Paris for the 22nd of December, then the Netherlands or wandering for the remainder of the trip. My question would be, what MUST I see? Are there any really good flight deals I need to look for ($700 to Paris is best I've seen)? And what is the real world situation on Hostels? I’m looking at a budget of about 2k including flight. Suggestions and tips would be great as I’ve never traveled civilian before.