I'v been there a handful of times, probably checked out 70% of the downtown coffee shops, they all have their different vibe so just walk around and pop into anyone you see.
I really don't remember the names of most of them, my top ones that I can name are:
Hill Street Blues - looks crazy in there, black light whiteout graffiti everywhere, if you can get a spot on one of the couches right by the window you can pretty much reach out and touch the canal.
Grey Area - not much of an atomosphere it's just where everyone goes to buy the best weed at the best price.
Grasshopper/Bulldog - they are a chain of coffee shops (bulldog was the very first one in amsterdam), there's a few of them around the city and they usually have several sections, like you can get weed, food, and booze all in the same building (sectioned off of course).
Barney's- Another popular one, has great hash selection, each table has a volcano vaporizer that is free to use.
There's tons more amazing coffee shops I can't think of now or forget the name just explore around don't go to the same one twice they are all very thematic.
And if you wanna do shrooms go to concious dreams and ask the shaman for advice, and don't go on the tourist attractions like the dungeon trippin on shrooms trust me not a good experience no matter how fun it may sound..
And no, marijuana is still legal to sell to tourists in amsteram, that law will never get passed in that city it generates wayyy too much revenue, you will be amazed at all the snacks and treats available for the stoned tourist, you can easily munch through a few hundred bucks a day hahah
