I would take two pairs of jeans: one for travelling in, one for going out in. If you do a weather check the day before and it transpires it will be warm, then swap the going out jeans for cotton trousers. Don't wear a maxi in Amsterdam. The idea of anything trailing on the floor in the city...........yeuch!
Flat shoes: one pair ballet flats, one pair sandals.
Top Shop had some great parka style lightweight rainmacs which fold down into handbag size for £20. None available on line now but try instore.
Avoid jeans or trousers that are over-long too - as per tulpe's comments re anything trailing on the floor in the city (you really don't want your clothes dragging along the pavement in Amsterdam - they have little 'weeing stations' in the street, but the wee doesn't always stay there, my jeans went white at the bottom and actually smelt of it!) It's a fab city though - jealous!
It should be fine if it's not raining! Re markets - I haven't been for a few years but there are just gorgeous little streets to wander down, with interesting shops and lovely places to have coffee and beers, or a smoke if that's what tickles your fancy!