This WiFi stuff is easy. First, to eliminate any further confusion, I'm going to recommend that you pick up a copy of the ARRL Antenna Builders Guide. Just Google "ARRL" and follow the clues. The purpose of this is to get the correct info into your hands about antenna construction. There are simple formulas you can use to figure out the "Hows and Whys" of antenna building.
OK, that being said, my next question is this: Are you going to build an Antenna or are you going to use a USB WiFi adapter with some sort of reflector? Your choice will make a huge difference.
If you go the USB adapter route, don't expect too much. All you're going to do is make some sort of rear-reflector for a simple 2-element beam-type antenna. Some moderate gains can be had with this method.
If you are wanting to build an actual antenna, like the real Cantenna (not the USB version), expect to invest some of your time into the building of these as they do involve some work and a little math but the gains are worth the work.
Also, don't forget that any real Antenna is just that, an ANTENNA! Nothing more. You will have to figure out how to connect your newly built antenna to your WiFi adapter and how to mount it for best performance. Tripods are very handy for desk-side testing.
The type and configuration of the antenna are up to you. Good Luck and have fun!
But do get the ARRL handbook. It will pay for itself!

get a pringles can and wrap the cylinder with aluminum foil, then cut a hole for your antenna

Its the called the parabolic focus and this would work better with parabolic cans in stead of radial ones, but no one makes parabolic cans so these will gain as much signal as possible.

parabolic focus is only for parabolic reflectors. the can would be similar to a concave mirror (reflector) which does have a focal point. its just not as focused as in a parabola. there would be a specific spot (usually half way between the center and edge(half the radius)) that would produce maximum boost.

but have u seen it in: SPED UP VIDEO FORM!? lol

lol