I went in June this year and it was fucking dope. Sun is up like 15 hours, everyone parties the whole time too. Odd going to sleep and wakig up when the sun is up.
but if its cheap you want ....go off season ..(i.e. when the kids are at school and less people are having holidays ...flights , trains, coaches atre all cheaper)
stay in one of the 10000 hostels in the city they are very cheap and if you research or just search hard enough you'll find one that suits your needs
For anyone looking for a peaceful & nature-minded camping area around Amsterdam, I would highly recommend the "Camping Zeeburg" area.
It's located at the outskirts of the city, about 10mins walk from a tram stop (last stop for tram no.10, if I recall correctly)
The place is like a normal camping area with a small shop, a bar (till 4am), laundry, showers, bicycle rental etc. There's cats, dogs, rabbits - hell, I even saw a rooster and some hens running around the place, free.
The staff is friendly and seems like some of them are drunk/stoned during working hours too
And above all, it's cheap. We (3 guys) stayed there with our own tents for a few nights and I think we payed like 7e/person/night. The bicycle rental is a MUST in A-dam. It's definetly the best way to get around there, and it's fun as hell.
Oh, and watch out for a coffeshop called "The Otherside". I thought the name was from a Doors song, but soon found out that the "other" side actually ment something totally different. After I noticed that the bar was full of male couples sitting together and the bartender was wearing some tight ass pink discoshirt I shoved the spacecake down my throat and bounced