^^I agree, a very trollable thread. But nitrous can me a tad confusing at first. Alright, to clarify...
There are basically 4 ways to do nitrous:
1.) Tank
If you're actually lucky enough to come across one, more power to ya. These are big $100^ tanks like they use in dentists offices. Not very easy to come by, generally used for parties and such. Never use a gas mask with one, you could suffocate.
2.) Whip Cream Dispenser $25-$60
A roughly 1 ft. tall metal container with a spout, you would expect to see one of these behind the counter at a coffee shop. They're intended to be reusable, so you can put you're own liquid cream filling in them, then screw in an N20 charger to pressurize it. For you're purposes you would leave out the cream altogether and just put in one or two chargers. It's pretty easy to load a double charger, and you'll notice the difference. Unless you're doing 2+ chargers, I consider balloons optional here, because it doesn't come out that cold. But if you take in more than half a charger at once, it's going to be mighty hard on your lungs. And balloons are nice in general because you can be breathing more nitrous than your lungs can hold at once.
3.)Cracker $6-$30
A common way to do budget whippeting, the cracker is a 2 piece metal tube that fits in the palm of your hand. You screw the pieces together to break the seal on the charger, then unscrew them to release the gas out one end. They aren't a bad option, but they can be tricky to operate, especially the cheap ones, which break sooner. They break more frequently than dispensers in general, and they can be a real pain when you're trying to dole out whippits to a large group. Also, these things are where it's REALLY important to use a balloon.
4.)The Lowly Whip Cream Can $1-$4 (More expensive in the long run)
Yeah, try it once, for sure. Then you'll be able to recognize the taste when you do a real whippit. There's not really enough gas in a grocery store can of whip cream to get much more than a taste. Figure roughly the equivalent of half a charger. Just forget the balloons here. Get the largest can you can find, hold it like it's sitting down, and take it all into your lungs. The whip cream won't come until it's empty, and it won't come that hard or fast. Basically, you just end your run with a nice taste of whip cream. Hopefully you're not allergic. When this is done, there will be no more propellant left in your can, hence no whip cream. You've basically got a big can of sweetened milk, which you're welcome to suck at. Sometimes the big cans will have enough pressure left for some cream.
If you can afford the dispenser that's great, but the cracker works fine. But you're definitely going to have a limited experience if you stick to the cans. If you can't figure out where to get this stuff, I'm going to tell you a little secret. Ebay. Yeah, seriously. If that information is to classified and risque to share on this lovely little site, then may the great moderator in the sky strike down this post.