There a couple different routes you can go, from storing kegs in a fridge and dispensing with picnic taps to buying or building a kegerator with a draft tower to converting a chest freezer (google “keezer”).
A few things you will need and some random info that may be helpful...
For a CO2 tank, you can buy a new shiny one or call your local Airgas (or similar) distributor and find out how much it is to join their program where you just swap out empty for full tanks when you run out of gas. I’d go with a 10 lb. tank if you have the space.
Then you need a regulator for the CO2 tank. There are a bunch to choose from, I have this one and am
happy with it: http://www.morebeer.com/products/taprite-dual-gauge-co2-regulator.html
Used kegs have gone up in price and down in quality over the last few years, but lower cost, good quality new kegs are now available at reasonable prices. Here are a few options: http://www.morebeer.com/products/torpedo-ball-lock-kegs.htmlhttps://beveragelements.com/beverage_elements_shop/kegs/new-ball-lock-kegs/5-gallon-ball-lock-keg-single-handle-new/https://beveragelements.com/beverage_elements_shop/kegs/5-gallon-ball-lock-keg-dual-handle-new/
The reason you only need one CO2 tank is because you can connect the regulator to a distributor similar to the one below. It’s nice to buy one with an extra port so you can purge kegs or rack beer when the other ports are occupied.http://www.northernbrewer.com/3-way-co2-distributor-w-1-4-mfl-shutoffs
I like the flared versions better than the barbed versions (for both the distributors and the keg disconnects).
From the distributor, you run gas lines to the kegs which connect to the gas disconnect. You’ll need one of each of these for each keg you are dispensing.http://www.morebeer.com/products/ball-lock-beverage-flare.html?site_id=9http://www.morebeer.com/products/ball-lock-gas-flare.html?site_id=9
You will also need gas and beverage tubing. I would get at least 5 feet of gas tubing for each keg, and longer for the extra port on your manifold so you have some reach when purging etc.
I would also get about 10 feet of 3/16” beverage tubing for each liquid connection. Read up on how to balance a draft system to prevent foaming (it isn't very complicated and there are a lot of resources on the web; use more beverage tubing than you think you need, it usually doesn't harm anything and you can always cut it shorter if you want).
To connect tubing to flared disconnects you need a barbed swivel nut, like this: http://www.northernbrewer.com/brewing/kegging/tubing/clamps-etc/barbed-swivel-nut-k123
Then you use a hose clamp to secure the tubing to the barbed swivel nut. You can use the regular worm gear style clamps, but I much prefer stepless ear clamps for permanent (or at least semi-permanent) connections. Buy a bunch of them.
They look like this: http://www.northernbrewer.com/stepless-clamp-no-145-oetiker
They do require a special clamper. You can often find them on Ebay or elsewhere for a decent prince. This is what it looks like (but don’t buy this one as you can get it for less than half somewhere else): https://www.amazon.com/Oetiker-14100083-Side-Jaw-formerly-Plastic-Coated/dp/B0037QFNJM
For any metal to metal connections you want to use a flared washer, like this: http://www.morebeer.com/products/flare-fitting-washer.html?site_id=9
You do not need flared washers for the connections to the disconnects, as the disconnects already have a built-in washer.
It's also a good idea to have a little keg lube on hand: http://www.morebeer.com/products/cip-film-keg-lube-4-oz.html?site_id=7