Amsterdam was incredible. Its expensive though, how long you stay all depends on your bankroll, how nice you want your lodgings, and how much weed you smoke. Food is expensive too. 3-4 days is the minimum you want to stay if you want to see most of what the dam has to offer, not weed related (van gogh museum, rembrandt, ann frank house etc.) I'd recommend about a week, if you get tired of the dam its a short train ride to rotterdam which is like a smaller chiller amsterdam (its got coffee shops as well) as well as belgium and such. Gotta travel with at least one person, I'd say no more then 3 (not including you) otherwise it gets to be a hassle getting everywhere. Don't take taxis either there expensive as hell. Take the tram.