Quick answer: Amsterdam runs about EUR 150 per day mid-range - noticeably less if you eat local and walk. Cheapest window: April-May for tulip season and September for mild weather - both avoid the peak summer crush on the canals.
What things actually cost
stroopwafel from a stall
3 EUR
beer at a brown cafe
6 EUR
tram single ride
3.40 EUR
Rijksmuseum entry
22.50 EUR
bike rental per day
14 EUR
canal cruise (1 hour)
18 EUR
Eat well for little
Fresh stroopwafel from a market stall - warm off the iron, about 3 EUR
Raw herring with onions from a haringhandel - the local rite of passage, about 4.50 EUR
Bitterballen with mustard at a brown cafe - about 8 EUR a plate with a beer alongside
Indonesian rijsttafel - a legacy of Dutch colonial history and a full-table feast, about 30 EUR per person
Apple pie at Winkel 43 in the Jordaan - about 6 EUR a slice, worth the queue
Money mistakes to avoid
Not booking the Anne Frank House online well in advance - tickets are released weeks ahead and there are no door sales
Walking in the bike lanes - they look like sidewalks but cyclists move fast and will not stop
Basing yourself around the Red Light District for convenience - it is loud until 3am; the Jordaan or De Pijp are 15 minutes away and far nicer
Renting a bike on day one without city-cycling experience - trams, taxis and locals share narrow lanes, so start on foot
Transport without the tourist tax
The train from Schiphol to Centraal takes about 15 minutes and costs around 4.60 EUR. The center is small enough to walk; trams fill the gaps (single ride about 3.40 EUR) and a GVB day pass is about 9 EUR.